Apparatus and Method for the Binding of Dust

ABSTRACT

The invention relates to an apparatus for the binding of dust, comprising a binder reservoir, which provides liquid binder which is under pressure, a binder line which is connected to the binder reservoir, wherein there is connected to the binder line at least one spray nozzle which may be located in the vicinity of a dust source. The apparatus is in particular so designed that large areas, which may extend over distances of several 100 m, may be supplied with binder, which may also be discharged, with these dimensions, in pulses at short intervals (1 second up to a few minutes).

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/094,818, filed on Oct. 18, 2018, which is a § 371 National PhaseApplication of International Application No. PCT/EP2017/075501, filed onOct. 6, 2017, now International Publication No. WO 2018/065586,published on Apr. 12, 2018, which International Application claimspriority to Austrian Application No. A 50903/2016, filed on Oct. 6,2016, German Application No. 20 2016 105 569.5, filed on Oct. 6, 2016,German Application No. 20 2016 105 570.9, filed on Oct. 6, 2016, andGerman Application No. 20 2016 105 572.5, filed on Oct. 6, 2016, all ofwhich are incorporated herein by reference in their entirety.

The present invention relates to an apparatus and a method for thebinding of dust. Known from DE 297 18 708 U1 and EP 0 908 215 A2respectively is an apparatus for the binding and/or the laying of dust.This apparatus is similar to a snow canon with an air jet, in which airis accelerated by means of a propeller or a rotor blade. In an air jetformed in this way, liquid is sprayed through one or more nozzles. Theliquid is thus conveyed by the air jet in a finely distributed form.With this apparatus, large amounts of water may be distributed over awide area.

Described in DE 1 658 345 U is a nozzle for the spraying of water or awater-air mixture for the suppression of dust in underground mining. Thenozzle is designed to be self-cleaning, by means of a part whichdetermines the outlet cross-section of the nozzle being subjected to aspring force. In the event of contamination of the nozzle there isexcess pressure, which is overcome by the spring force. This enlargesthe nozzle opening, and self-cleaning of the nozzle is effected.

Disclosed in German utility model DE 1 668 644 U is an apparatus for thesuppression of dust from gases, in which steam of fine particles is usedto envelop the dust particles.

Disclosed in WO 2014/019311 A1 is a further nozzle for the spraying ofwater, to remove and cool down dust from mining machinery. The water isdistributed as finely as possible by means of an airflow.

Described in DE 915 203 B is a further method and a further device forthe suppression of dust. A pipe system is provided with nozzles, fromeach of which a partial flow of a mixture of air and liquid is branchedoff. With each branching, the mix ratio between air and liquid isvaried. This is used purposefully to vary along the pipe system theexiting mix ratio of fog in spray mist.

Described in EP 0 950 796 A1 is a spray mist unit for the suppression ofdust, in which an air jet is mixed with water at one or more mixingnozzles. The mixing nozzles are located as close as possible to the dustoriginating points.

Described in DE 23 35 861 A1 is an apparatus for feeding into acylindrical silo bulk material which easily becomes dusty. On being fedinto the silo, the bulk material is wetted by a dust binder, whichinvolves it being sprayed with the dust binder. The binder is water withthe addition of a water-surface-relaxing substance.

Disclosed in DE 6 812 095 U is a further apparatus for the suppressionof dust, in which the dust-creating substance is sprayed with water.

DE 1 815 543 relates to a device for the suppression of dust from coalextraction involving cutting and stripping. Here the direct point ofdust origin and its closer environment should always be covered by awater screen. A mining machine is always in the area of a group ofnozzles, by which it is covered with a water screen.

DE 41 31 75 A1 discloses a stripping lane spray system in which astripping lane may be sprayed by several nozzles. This spray system ischaracterised by the fact that the nozzles assigned to an extractionframe are fed via a separate control valve and several spray zones ofvarying size may be formed. This should make it possible to adapt thespray zones to the respective conditions in an optimal manner and with areduction in water consumption, since only as many nozzles are switchedon are fed as are required for the greatest possible binding of dust.

Disclosed in DE 1 795 74 U is an apparatus for the suppression of thedust floating in the air, which has a washer which sucks in thedust-containing air and sprays it with water inside the washer, so thatthe dust is bound.

Described in AT 512 490 A1 is a high-pressure fog machine which may beused for, amongst other things, the binding of dust. The purpose of thishigh-pressure fog machine is to produce fog which is capable offloating. Water, in particular drinking water, is fed to sprayingorifices, at which the water is sprayed out, under pressure of around70-100 bar. By means of switchable valves, several zones may be providedand supplied with fog independently.

Disclosed by DE 34 41 386 A1 is a method for the suppression of dust.This uses a foam cannon which provides foam for binding the dust.

Disclosed in WO 2008/082316 A2 and WO 2008/020773 A1 respectively are,in each case, spray nozzles from which water may be sprayed. These spraynozzles are provided especially for various purposes in mining,including control of dusty conditions.

WO 2011/095463 A2 discloses a spray nozzle unit, in particular for thespraying of areas at risk of explosion in underground mining, and foruse in ultra high speed fire suppression systems, with response times ofless than 50 ms. This spray nozzle unit comprises a nozzle body with anozzle opening for the release of spray fluid.

Disclosed by US 2007/0125558 A1 is an apparatus for the binding of dust.This apparatus includes a supply tank for binder, wherein pumps may bedriven by means of an optical sensor to convey binder from the bindersupply tank and to discharge it accordingly. In this connection it isprovided in particular for the pump or pumps to pump binder out of thesupply tank and to discharge it via the relevant nozzles.

Disclosed in WO 2014/161023 A1 is a dust binding apparatus forcontainers. According to this apparatus it is provided that bindershould be conveyed from an external supply tank and discharged through acorresponding pipe system by means of pumps into a container above adust-generating medium, so as to bind the dust in this way.

DE 20 2015 104 984 U1 discloses an apparatus for the removal of floatingdust, in particular fine dust, from the environmental air of a transportinfrastructure. This apparatus include e.g. a spray unit with a pressuregenerator to provide a pressure difference. The spray unit presses orsucks liquid solution out of an intermediate container which is fed viaa supply line, not shown. Here it is provided, by means of the sprayunits, to transfer the liquid solution from the ground, at the height ofwhich each intermediate container is approximately mounted, into anelongated spray line. Nozzles are arranged along the length of the sprayline, and from these nozzles the liquid solution is sprayed in drop forminto the environmental air.

DE 75 35 462 U discloses a control unit for the switch operation ofspray nozzles for the suppression of dust in mining operation. Thisinvolves the provision of spray nozzles which may be switched on and offindividually using a lever or in groups by means of suitable controlvalves. Here a control unit may be used for remote control of thecontrol valves by means of suitable switching devices. The spray nozzlesshould be controlled in such a way that the dust, irrespective of theoperating speed of a mining machine, is effectively suppressed directlyat the point of origin, i.e. in the operating area of the miningmachine.

Disclosed in DE 18 15 543 A is a device for the suppression of dust.This involves the provision of a multiplicity of nozzles, combined intojointly operable groups in such a way that the respective group areasintersect, so that in each case that nozzle group may be operated withinwhich the mining machine is located, in order to suppress the dustproduced by the mining machine.

U.S. Pat. No. 2,722,456 A discloses a spraying apparatus which includesa supply tank. Connected to the supply tank via a line is a pump forextracting spray medium from the supply tank. The pump may be in theform of a gear pump. Also connected to the pump is a line to which arefitted several nozzles for discharge of the spray medium. Also providedis a valve to control the output of the spray medium. The volumetricflow of the spray medium taken from the supply tank may be set by meansof a further valve. Also described in the application is that the spraymedium is conveyed to the nozzles by means of a pressure generated bythe pump. In addition, another line branches off from the line into thesupply tank, to which corresponding nozzles are connected, in order toagitate, mix and stir the spray medium.

Disclosed in EP 1 084 607 A1 is a movable storage unit. This storageunit includes a pressure vessel which contains means for exertingcompressive forces on the water held in the pressure vessel. The meansfor exerting compressive forces may here be provided in the pressurevessel itself or on the pressure vessel, e.g. by a pressure equalisingvessel. According to an embodiment, the pressure vessel has a deformablediaphragm which divides the pressure vessel into a bottom chamber and atop chamber. The bottom chamber may be filled with water via a line andthen reduces the top chamber, in which is provided a coil spring topressurize the diaphragm. Instead of the coil spring, an inert gas suchas nitrogen or carbon dioxide may be used as compressible pressuremedium in the chamber. There a discharge fitting is directed on to theareas to be watered, and opened. Provided for discharge is preferably aspray nozzle with upstream operating valve 32.

Disclosed in DE 000P0047416MAZ is an overhead sprinkler system withautomatically operating shutoff device. This overhead sprinkler systemis designed e.g. for sprinkling three different sprinkling zones I, IIand III.

Disclosed in DE 75 35 462 U is a control unit for the switch operationof spray nozzles for the suppression of dust in mining operations, inorder to spray a mining area.

In DD 2 58 837 A1, a method and an arrangement for the creation oflarge-scale dust barriers are disclosed.

U.S. Pat. No. 479,979 A discloses a spraying apparatus.

Disclosed in DE 18 33 442 U is an “ambulant” transferable system for thesprinkling of agricultural areas.

DE 380 896 discloses an overhead sprinkler system with branch linescoming off a field line.

Disclosed in DE 19 28 789 C is an installation for the sprinkling ofwater or fertilizer in greenhouses.

Disclosed in US 2014/0239080 A1 is an immovable installed overheadsprinkler system.

From “Technische Stroemungslehre [Technical Fluid Mechanics], LeopoldBoeswirth, Text and Exercise Book, 8^(th) edition, Vieweg+Teubner,Chapter 12.3, it is known that, in the case of long pipelines throughwhich liquid flows, the pressure on a slide which is opened or closed,may suddenly rise or fall sharply. It may even lead to vapor formationon the outflow side. Pressure shocks are reflected in the line systemand lead to pressure oscillations. Such pressure shocks may considerablyimpair the life of apparatus with fluid-conveying lines.

To summarize, it may be stated that, for the binding of dust

1. an air/water mixture is often used to atomize the water forlarge-scale distribution

2. a fog or spray mist is provided as close as possible to thedust-originating point, in order to bind the dust, and

3. different dust binders, such as spray mist, fog, foam with andwithout chemical additives, are used.

A problem of the present invention is to create an apparatus and amethod for the binding of dust, with which dust may be bound with greatefficiency.

A further problem of the present invention is to create an apparatus anda method for the binding of dust, with which dust may be bound reliablywith the least possible amount of binding agent.

A further problem of the present invention is to create an apparatus anda method for the binding of dust, wherein the apparatus and/or theapparatus used under this method is or are subject to minimal wear.

A further problem of the present invention is to create an apparatus anda method for the binding of dust, with which the escape of dust may bereliably prevented or considerably reduced along a large section or alarge area, as for example a section of road or a gravel pit.

A further problem of the present invention is to create an apparatus anda method for the binding of dust which may be attached to or integratedwith a wide variety of machines and vehicles, such as e.g.stone-crushers, track-laying machines, asphalt planers, cleaningvehicles, etc., wherein mobile operation is also possible.

One or more of the problems described here is or are solved by thesubjects specified in the independent claims. Advantageous developmentsare set out in the relevant dependent claims.

The binding of dust may in principle be effected by an artificial fog orby a spray mist. In the case of an artificial fog, a fog which settlesslowly on the ground is generated, with the dust being washed out of theair by the fog droplets. With the spray mist, the ground is wetted withbinder, so that the emergence of dust is prevented. The fog formationand the spray mist differ mainly in droplet size, with the transitionbeing fluid. The generation of a fog also leads to wetting of the groundand the generation of a spray mist also leads to dust being washed outof the air. However, in the case of an artificial fog, the main emphasisis on the effect in washing dust out of the air, while for spray mist itlies in the wetting of the ground. Artificial fog comprises dropletswith a size of less than 200 μm, in particular less than 150 μm or lessthan 100 μm. Spray mist comprises droplets with a size of at least 100μm, in particular at least 150 μm and preferably at least 200 μm.

In the case of an apparatus in which the ground is wetted with spraymist, preferably no more than 6 l/m²/h and preferably no more than 4l/m²/h and in particular no more than 3 l/m²/h of binder are delivered.This ensures that no puddles occur. For sealed ground, the amountdelivered should be set lower than for unsealed ground. The amount ofbinder delivered should be at least 0.75 l/m²/h and preferably at least1 l/m²/h or in particular at least 1.2 l/m²/h, to ensure adequatewetting of the ground. These values for the delivery of binder apply tocontinuous operation. For interval operation, the amounts delivered arecorrespondingly reduced by the pause times.

The apparatus variants described below for the control and directing ofbinder flows may be used for the generation of both fog and spray mist,unless expressly otherwise stated.

According to a first aspect of the present invention, an apparatus forthe binding of dust is provided, comprising:

a binder reservoir, which provides liquid binder which is underpressure,

a binder line which is connected to the binder reservoir, wherein thereis connected to the binder line at least one spray nozzle which may belocated in the vicinity of a dust source.

The spray nozzle is located in the vicinity of the dust source, and ispreferably so designed and mounted that it is not the dust source whichis sprayed with binder, but instead a binder fog is formed at apredetermined distance from the dust source. This arrangement is basedon the knowledge that dust is swirled up at a dust source, while a dustsource is generally linked to a turbulent airflow. If one wished to binddust in such a turbulent airflow using a binder, then the binderrequirement would be considerable. If on the other hand the dust isbound at points further from the dust source, at which the airflow hassettled down, then the dust spends longer in the air and may be boundreliably with significantly fewer fog droplets than at the dust sourceitself. Even if a local dust source is surrounded by an artificial fogwall at a distance, the binder requirement is much lower than when thedust source is sprayed directly with binder, even though the area inwhich the fog is artificially formed is generally much greater than thedust source, since it surrounds the dust source at a predetermineddistance.

The distance should be selected so that, in the area of the fog, theairflow containing the dust has calmed down sufficiently that the fogcan sink slowly to the ground and is not moved away uncontrollably.Usually a distance of some 10 cm, preferably at least 50 cm or at least1 m or at least 2 m is to be maintained. In choosing a suitabledistance, external airflows should also be taken into account, such asmay be created by movements of goods, vehicles, wind or thermal effects.Thermal effects often occur in sheds. It may be expedient to provide oneor more baffles, by which an airflow contaminated with dust is sodirected that it calms down and an artificial fog can remove the dustefficiently.

The distance from the dust source should preferably be chosen so thatthe fog occurs mainly in an area in which the airflow does not exceed 1m/s, in particular does not exceed 0.8 m/s or does not exceed 0.7 m/sand preferably does not exceed 0.5 m/s. It has been found that, with anairflow greater than 1 m/s, the dust cannot be bound efficiently by afog, or the amounts of water needed for efficient dust binding riseexponentially. The airflows may vary over place and time. In theunloading of large rocks, for example, a very strong airflow may occurtemporarily, while in the pauses between the individual unloadingoperations, the airflow is significantly weaker. Short periods in whichthe limit values for maximum airflow are exceeded impair dust bindingefficiency to only a limited extent. Baffles may be provided to keepextraneous airflows away from the fog zone, so as to maintain the limitvalues described above for the airflow in the area of the fog.

The binder is a liquid binder, preferably water. In the prior art, anair/water mixture is often used. Such an air/water mixture is howeverdisadvantageous, since the air content generates a high inherentairflow, which is not suitable for the formation of a floating fog. Anair/water mixture may be used to produce a spray mist wherein, however,water is preferred which is driven by a spray nozzle without air.

The binder is made available in the binder reservoir at a pressure ofpreferably maximum 10 bar, in particular preferably maximum 7 bar and inparticular not more than 5 bar. The lower the pressure, the easier it isto design an apparatus with a long binder line, which permits wide-areacoverage with spray mist. At higher pressure there is the risk thatindividual components, in the long term, will not withstand the loading,and the overall regulation and control of the pressure in the binderline will become significantly more expensive and more complex.

The binder reservoir should make the binder available at a pressure ofat least 2 bar, preferably at least 3 bar and in particular preferablyat least 4 bar. The higher the pressure in the binder reservoir, thegreater the pressure losses in the binder line can be, while stillproviding an adequate pressure at the spray nozzle or nozzles. This alsomeans that, the greater the pressure at the binder reservoir, the longerthe binder line may be without needing an additional pressure stage inthe form of a pump. The binder reservoir may be a well, a tank with orwithout a feed pump, or a connection to a water pipe, which provides thebinder with water at a predetermined pressure.

The pressure under which the binder reservoir or a binder source is madeavailable is preferably set by a pump. The pressure may however also bepreset by an available water supply or an elevated tank which provideadequate pressure through a suitable geodetic difference in height, sothat no extra pump is needed to convey the binder from the binderreservoir.

Limitation of pressure to a maximum value in the range of 5 to 10 baralso has the advantage that the binder line may be formed by a flexibletube, for example a plastic tube, in particular a PE tube. Such flexibletubes have considerable advantages since on the one hand they can bufferpressure, connection points for spray nozzles may be punched out atdesired points, and in addition they can be laid very quickly andeasily.

A further benefit from the limiting of pressure is that no high-pressurepumps, which are susceptible to polluted air, are necessary.High-pressure pumps are pumps which generate a continuous operatingpressure of 20 bar or more.

The spray nozzle or nozzles are so designed that the binder is sprayedwith a droplet size of 30 to 120 μm and preferably 50 to 150 μm and inparticular with a droplet size of 60 to 90 μm. In calm air, such adroplet size forms a floating fog which reliably binds the dust andgradually sinks down.

According to a second aspect of the present invention, the binder linemay extend over a distance of at least 100 m or in particular at least300 m, with several spray nozzles connected to the binder line alongthis length, and wherein the apparatus is so designed that no more than6 l/m²/h of binder is discharged onto the ground during a sprayingoperation.

The amount of sprayed binder is preferably set so that there is aminimal excess of moisture, i.e. not the whole of the sprayed binder istaken up by the air, but liquid fog particles are present in the air.Such fog particles sink, binding the dust contained in the air, andtransporting it to the ground. Preferably the amount of water output isso large that an adequately strong downwards movement takes place, inorder to transport the dust rapidly downwards. A certain excess ofbinder reduces the standard cost. It is however possible with such adroplet size to set the amount of sprayed binder so that on the one handa stable floating fog is provided, and on the other hand the amount ofbinder is so small that no puddles occur on the ground. The apparatusunits for producing artificial fog are preferably so designed thataround 5 to 30 liters of binder are discharged per nozzle per hour, withthe binder being distributed over an area of 0.8 m to 1.5 m around thenozzle. The spray nozzle or nozzles is or are preferably a pressurenozzle or nozzles, which is or are designed with an automaticallyclosing or opening pressure control valve and therefore openautomatically from a certain opening pressure of the fed binder upwards.The apparatus has a pressure control, by which the pressure in thebinder line may be controlled. By this means it is possible to monitorvia the pressure control whether the one or more spray nozzles aredischarging binder or not.

In particular it is provided according to the first aspect that thebinder line may have one or more pressure control valves, which, aspressure switching valves, open from a predetermined switching pressureupwards and thus release a binder feed to the spray nozzle(s), or, aspressure regulating valves, also open from a predetermined switchingpressure upwards and at the same time regulate a pressure on the outflowside of the pressure regulating valve to a predetermined pressure range.The benefits of suitable pressure nozzles or suitable pressure controlvalves which, as pressure control valves, open from a predeterminedswitching pressure upwards and thus release a binder feed to the spraynozzle(s), or, as pressure regulating valves, also open from apredetermined switching pressure upwards and at the same time regulate apressure on the outflow side of the pressure regulating valve to apredetermined pressure range, are indicated below and will be explainedin more detail with the aid of a suitable embodiment.

The pressure nozzles or the pressure control valves may be designed forexample with an opening pressure of 2 bar, 3 bar or 4 bar. The closingpressure is preferably somewhat less than the opening pressure. For anopening pressure of 2 bar, the closing pressure is for example 0.9 bar,for an opening pressure of 3 bar for example 1.5 bar, and for an openingpressure of 4 bar for example 1.8 bar. By this means it is ensured that,due to the pressure drop generated after opening of the respectivenozzle, the pressure nozzle does not immediately reclose, but insteadcan continue to be held open at a lower pressure.

Such pressure nozzles and pressure control valves respectively allowsimple central control via the binder pressure, since the pressurecontrol valves open and close completely when the pressure in the binderline is suitably controlled. Moreover, such automatically closingpressure nozzles and pressure control valves prevent draining of thebinder line, since, in the event of a pressure drop, they closeautomatically under the switching pressure. By this means, the pressurein the binder line does not fall, or perhaps only very slowly so that,with pulses at intervals, no or only very slight pressure must be builtup in the binder line. These pressure nozzles therefore function also asrun-out stops. This provides the following benefits:

-   -   The binder line need not be filled, before fresh water is        discharged through the spray nozzles. Between individual pulses,        however, a small amount of binder must be fed in. Due to the        pressurized binder reservoir, this binder is suddenly made        available and already under pressure. This makes possible rapid        pulsing with a minimal amount of discharge.    -   Pressurized water is therefore always available directly at the        spray nozzles or the adjacent pressure nozzles or pressure        control valves.    -   Refilling of the binder line is subject to the risk of pressure        shocks and cavitation in the line and nozzles and other        components such as pumps, valves, etc. There is also the risk of        sucking in unclean ambient air or polluted drainage water or        other dirt. This risk is avoided or at least reduced.

The pressure nozzles may be designed with integral pressure valves witha predetermined opening and a predetermined closing pressure. Thepressure nozzles may however also be formed by a nozzle and a separateupstream pressure valve.

The pressure nozzles preferably have a diaphragm which is acted on by apiston pre-loaded by a spring, so that passage through the pressurenozzle is opened only from a predetermined opening pressure onwards andis closed again when the closing pressure is reached. The pressurenozzles are preferably set so that, in the whole of the dust binderapparatus or in certain sections in which substantially identical spraynozzles are preset, they provide a pressure to the respective spraynozzles, which varies by a maximum of 20% and in particular a maximum of10%. Such an even pressurization results in an even output of binder,wherein the uniformity here relates both to the geometry of therespective spray cone of the individual spray nozzles and also to theamount of binder discharged. It is especially expedient to provideroughly the same pressure in sections of the dust binder apparatus inwhich the identical nozzles are located. Naturally, differentlyconfigured sections, such as, for example, sections in which standingnozzles are provided for wetting the ground, may be provided with adifferent pressure to, for example, sections with suspended nozzles forcreating a fog, and accordingly with pressure nozzles which areotherwise set or otherwise designed or with otherwise designed pressurecontrol valves.

Output of binder at differing levels of intensity is set preferably bythe spacing of consecutive spray nozzles and not by differences inpressure. The spray nozzles are preferably so designed that they sprayout the binder with a circular or semi-circular throwing cone. Thespacing of two consecutive nozzles amounts preferably to the diameter Dof the circle of the relevant throwing cone less at least 20%(corresponding to 0.8D) and in particular at least 34% (corresponding to0.66D) of this diameter. By this means a roughly strip-shaped area isevenly covered with binder, wherein the overlapping sections of adjacentthrowing cones are limited. Preferably the spacing of adjacent nozzleslies in the range of the diameter of the throwing cone less at least 45%and preferably at least 50% of the diameter. In the case ofsemi-circular throwing cones, the closer spacing of the nozzles with atleast 45% deduction from the diameter is preferred. Dust binderapparatus units which create fog generally have a nozzle arrangementwith maximum intervals of 0.55D or 0.5D.

The pressure control has preferably a control valve which is located inthe binder line in the area between the binder reservoir and thepressure nozzle or nozzles, wherein the control valve may be operated bya control unit. By this means the spray nozzle or nozzles may be fedspecifically with binder at a predetermined pressure. It is alsopossible to provide several control valves, each downstream of one ormore spray nozzles, which are then supplied with binder at apredetermined pressure by means of the respective control valve in eachcase. The control valves may be driven by the control unit by hydraulic,pneumatic or electrical or mechanical means.

The spray nozzle or nozzles may also be provided with a valve operabledirectly by a control unit. The apparatus may also include spray nozzlesin the form of pressure nozzles and spray nozzles provided with adirectly operable valve. Such directly operable valves may be opened andclosed remotely by the control unit.

The binder reservoir or a pressure reservoir may include a pressurevessel with gas cushion. Such a pressure vessel with gas cushion may bein the form of a diaphragm vessel which has a diaphragm dividing thediaphragm vessel into a gas pressure chamber and a binder chamber. Thepressure vessel may also be a wind vessel in which there is a gas bubblewhich is in direct contact with the binder. Since gas may be compressed,binder may be taken up in the pressure vessel with gas cushion, whereinthe gas is compressed in the gas pressure chamber, so that the binder isstored with increasing pressure in the pressure vessel with gas cushion.With one or more such pressure vessels with gas cushion, dynamicvariations in pressure may be reduced. Such dynamic pressure changesoccur due to variations in flow rate on account of the inertia of theliquid. Such changes are unavoidable as a result of start-up andshutdown or switch-off processes. In particular the rapid change inthroughflow and therefore of velocity in a pressure line, for examplethrough fast closing or opening of shut-off devices or through suddenpump stoppage, generates pressure shocks in the lines. Pressure thenswings up and down around the initial pressure. At the end of the linethe pressure wave is reflected, returns to the starting point as anegative wave, and dies away gradually in multiple to-and-fro movements.As a result of partial vacuum, this may even lead to breaking off of thewater column. The resultant collision of the two independentlyoscillating flows leads to especially dangerous pressure shocks. Inprinciple, opening and closing times of shutoff devices may be extended,so that the change in velocity takes place harmlessly. There are howeverunavoidable operational events such as sudden pump stoppage or powerfailure or an emergency stop. With the pressure vessel with gas cushion,such pressure shocks may be reduced, since, for example, in the event ofa sudden closing of a shutdown device, the pressure vessel with gascushion continues to accept binder, so long as it is located in the flowdirection upstream of the shutdown device, and a gradual rise inpressure in the binder line occurs. With a sudden failure of a pump, thepressure vessel with gas cushion supplies further binder, so that theliquid column formed by the binder is not stopped abruptly. If,moreover, a pressure vessel with gas cushion is fitted before the pumpor at the pump inlet, this vessel may be used as additional protectionfor the pump or the upstream hydraulic elements, since it can equalizefeed fluctuations and dampen pressure shocks. The binder feed to thispump must stand below a certain pressure, since otherwise the pressurevessel would become empty.

The apparatus may also have several pressure vessels with gas cushion.The pressure vessels with gas cushion may be arranged distributed alongthe binder line. The volume of the pressure vessel or vessels with gascushion may amount to at least 300 l, preferably at least 1,000 l, inparticular at least 5,000 l and preferably at least 10,000 l or several10,000 l. The volume of the pressure vessel with gas cushion comprisesboth the volume of the gas pressure chamber and also the volume of thebinder chamber. The binder chamber generally amounts to around 20% to50% of the total volume of the pressure vessel. In the normal state ofthe apparatus, the pressure in the gas pressure chamber should be around0.5 to 0.9 times the operating pressure or a start-up pressure of adelivery pump.

Especially preferred is for one or more pressure vessels with gascushion to be used with a dust binding apparatus which idles duringstandstill or pause periods. These are in particular dust bindingapparatus units which have no or only few self-locking pressure controlvalves which act as anti-overflow devices. During a stoppage or a pause,the lines of this dust binding apparatus empty partly or completely. Onresumption of operation, the lines are first filled with binder. Here,the property of the pressure vessel with gas cushion is advantageoussince it first delivers binder rapidly into the line at high pressurewhile, owing to the expansion of the gas cushion, the pressure in thepressure vessel decreases, causing the delivery pressure to reduceaccordingly. With almost complete filling of the lines there is then areduced pressure, thereby reducing the problem of pressure shock.

In a dust binding apparatus it is possible to provide differentsections, which drain at different rates during a stoppage. Theindividual sections may each be provided with a separate pressurevessel, if this is expedient. Especially the sections which drainquickly are preferably provided with a pressure vessel, so that they maybe rapidly refilled once again.

The pressure vessel with gas cushion preferably has a feed line forfilling the pressure vessel with gas cushion and a discharge line fordraining the pressure vessel with gas cushion, wherein the feed line hasa narrower cross-section than the discharge line, so that filling of thepressure vessel with gas cushion takes place at a slower rate thanemptying of the pressure vessel with gas cushion. By this means it ispossible for pressure peaks, resulting from rapid braking of the binderin the pipeline, to be absorbed gradually, distributed over a longerperiod of time. The slow filling of the pressure vessel with gas cushiontherefore leads to a gradual braking of the binder fluid column. Such adesign of the pressure vessel with gas cushion is also suitable forreliably capturing downwards directed flows. On the other hand, in theevent of a pump failure, a large binder flow can be provided veryquickly, so that a corresponding pressure shock is avoided. In addition,through various mechanisms and/or depending on the respectivelyprevailing operating pressures, both the duration of filling of thepressure vessel or vessels with gas cushion, and also the duration ofemptying, may be influenced.

Instead of or in combination with the cross-section narrowing, anotherflow resistance may be provided in the feed line. The flow resistancemay be for example in the form of a pressure reducer, a pressure plateor a difference in height. If the pressure vessel with gas cushion islocated a short distance above the binder line, preferably severalmeters above the binder line, then the binder must be conveyed upwardsagainst the force of gravity to fill the pressure vessel with gascushion, and on draining the pressure vessel with gas cushion may beconveyed quickly into the binder line due to the force of gravity. Ifthe delay in filling and the acceleration on draining are effectedsolely due to such a difference in height, then the feed line and thedischarge line may be in the form of a common pipe run. In using such aheight difference it is expedient if the cross-section of the feed lineand the discharge line is large, so that the liquid wave leading fromthe binder line to the pressure vessel with gas cushion has a highweight.

As already explained above, automatically closing pressure nozzles whichact as run-out stops allow interval operation, since water underpressure is always directly present at the spray nozzles or the pressurenozzles adjacent to the former. Also advantageous for interval operationis the provision of one or more pressure vessels, since draining isoften not completely prevented even with automatically closing pressurenozzles. The automatically closing pressure nozzles frequently lead tovery slow draining, so that refilling at the start of a spray intervalmay be effected very quickly by means of a pressure vessel with gascushion.

This use of automatically closing pressure nozzles or the use ofautomatically closing control valves in conjunction with one or morepressure vessels effects very short reaction times for the spraying ofbinder after a spray pause. The reaction time is measured after a pauseof at least 5 min from switching on a pump or opening a valve, so that asection in which spray nozzles are located is supplied with binder whichis under pressure until the point in time at which all nozzles suppliedwith binder through switching on the pump or opening the valve aredischarging binder. With prototypes, reaction times of just a fewseconds have been obtained, even when the section was longer than 100 m.Dust binding apparatus units for producing fog are preferably sodesigned that their reaction time does not exceed 10 s and in particularis no greater than 5 s, while dust binding apparatus units for wettingthe ground are preferably so designed that their reaction time is nogreater than 2 min and in particular no greater than 1 min andpreferably does not exceed 30 s. Such short reaction times may beachieved even with large dust binding apparatus units with sections witha length of more than 100 m and in particular more than 300 m.

Also required for interval operation are flexible lines, which can alsostore binder under pressure.

The apparatus preferably has a pump, which pumps the binder. A pressureswitch which may be connected to the binder line switches on the pump atthe start-up time, when a predetermined start-up pressure has beenundershot. In this way, a predetermined minimum pressure is maintainedin the binder line automatically.

Several pressure switches may also be used, being assigned differentfunctions or having different start-up pressures. These functions arefor example:

Pressure switch 1: switch pump on/off

Pressure switch 2: monitor excess pressure

Pressure switch 3: monitor under-pressure (such as may occur e.g. duringdry running)

Pressure switch 4: line end pressure monitoring: if at the end of theline there is no pressure or too little pressure, this may suggest aline breakage or a blockage; or also checking whether a desired pipelinepressure reduction (e.g. before a pump stop) has already reached theend.

Pressure switch 5: monitor suction line for correct under-pressurevalue. This is an indicator that the pump is sucking in, and also anindicator of whether or not the suction force of the pump is in theright direction (avoidance of cavitation), or an indicator of a suctionline blockage or a suction line pre-filter.

Pressure switch 6: gas pressure monitoring of the pressure vessel withgas cushion.

Pressure switch 7: pressure vessel filling status. Only when, incontinuous operation, the pressure in the pressure vessel or in its feedline or the main line is roughly constant, can a full pressure vessel beassumed. May be used e.g. to reach a decision as to whether a pump mayalready be switched off or should run on, in order to buffer in thepressure vessel.

Pressure switches 8 and 9: pressure difference evaluation,pre-/post-filter pressure. To monitor filter status, whether this e.g.is producing too much loss of pressure due to dirt accumulation andrequires cleaning. An automated filter cleaning process may be startedor also just a report made that the pressure difference is too large andthat cleaning should take place.

These pressure switches need not all be constantly active; they may alsobe “conditioned”. E.g. the under-pressure switch is used only duringcontinuous pump operation to monitor possible under-pressure.

The pressure switches may also be equipped with two switching points(lower and upper), in order to create certain hystereses which allow thesystem to run more stably and more quietly, since not every small changein status leads immediately to a switching process, but instead acertain threshold must first be exceeded. In this way the system runsmore stably and does not start to cycle or oscillate. In addition, thepressure switches may be coupled to timers (e.g. time relays) so that,on reaching a switching point, first only the timer is activated and,only after the stored time has elapsed does the switching process becomeeffective.

The pressure switches may either trigger direct processes or also actsimply as detectors. For checking the correct function, visual pressureindicators may also be fitted or connected temporarily in the vicinityof the pressure switches, e.g. pressure gauges or remotely transmittingpressure transmitters.

The pressure switch may also be so designed that, on exceeding apredetermined switch-off pressure, the switch-off time, the pumpswitches off and/or an emergency release valve opens. A flow meter mayalso be connected to the binder line in such a way that, if the flowrate falls below a predetermined minimum level, the pump switches offand/or an emergency release valve is opened. In this way it is ensuredautomatically that the pressure in the binder line does not rise toomuch.

With a target value or other flow measuring device it is also possibleto determine an excessively large flow (=abnormal operating status, e.g.line breakage). Expediently, this flow measurement is time-based, i.e.only after a certain stabilization phase after start-up of the unit(during the start-up phase, for example, abnormal conditions may prevailfor a short time) does the measured value of the flow sensor apply. Thismay also be coupled to the condition that, for example, the flow rateovershoot is maintained for a certain minimum period of time.

A switch-off delay device may be provided, which allows the pump to beswitched off only after the expiry of a predetermined delay timeinterval, wherein the delay time interval starts with the switch-on timeor the switch-off time or a point in time between the switch-on time andthe switch-off time. Such a switch-off delay device prevents short-termpressure or volume fluctuations leading to shutdown of the pump, whichwould lead to further variations in pressure. The change in state, i.e.the pressure drop or the reduction in flow must therefore last for acertain period of time before the pump is switched. The delay timeinterval is preferably at least 5 seconds, preferably at least 15seconds and in particular at least 30 seconds.

An overpressure pressure switch may be connected to the binder line andswitches off the pump and/or opens an emergency release valve ondetecting a certain overpressure which exceeds the switch-of pressure.The switching on account of detection of overpressure by means of theoverpressure switch overrides preferably all other control processessuch as, for example, not switching off due to a continuing delay timeinterval. In addition, signaling/an alarm indication/initiation of alarmresponse measures such as e.g. additional disconnection of the binderfeed may be effected.

The apparatus is preferably designed so that the flow velocity of thebinder in the lines does not exceed 5 m/s and is preferably no greaterthan 3 m/s. The greater the flow velocity, the greater the pressurelosses. The pressure losses are proportional to the square of the flowvelocity. In practice these upper limits have proved to be veryadvantageous, since, at these flow rates, it is possible to supplyseveral spray nozzles reliably over a long section (e.g. 1 to 5 km) withsensible line cross-sections. At higher flow rates, problems withpressure shocks may arise.

The binder line may have a main run, and a secondary run, runningparallel to the main run and with a smaller cross-section, wherein thesecondary run joins the main run at both ends, and a flow meter isprovided in the secondary run. The throughflow measured in the secondaryrun is proportional to the throughflow in the main run or main flow,therefore making possible the deduction of the overall volumetric flowthrough the main run and the secondary run. Measurement of the lowervolumetric flow in the secondary run is much simpler than measuring themuch greater volumetric flow in the main run.

The flow meter may be so designed that it measures the flow indirectlywith the aid of the temperature of the binder in the pump or in thedirection of flow shortly after the pump and/or with the aid of thecurrent consumption of the pump and/or with the aid of the pressuredifference before/after the pump, and/or with the aid of the pressurebefore the pump and/or with the aid of the pressure after the pumpand/or with the aid of the acoustics of the pump and/or with the aid ofthe current power consumption of the pump shaft. Since the pumpgenerates heat and the binder is often provided from a cool reservoir,such as, for example, a well, a conclusion may be reached, with the aidof the temperature of the binder in the pump or in the flow directionshortly after the pump, as to the volumetric flow of the binder in thebinder line or in the pump.

The binder line may be provided with a venting device, which expels airbubbles from the binder line to the outside. Such air bubbles may occurthrough outgassing of the binder due to pressure variations. The ventingdevice may be a passive vent valve which is permeable to gas andimpermeable to liquids. The venting device may also be a switchablevalve, located in the binder line. If a gas bubble is present, theswitchable valve is opened by a control device. The presence of a gasbubble may be detected by the control device on the basis of certainoperating states and/or by means of a sensor. The predeterminedoperating states detectable by the control device are, for example, astoppage of delivery or a low pump load on start-up. Gas bubbles may bedetermined by means of temperature sensors or pressure sensors orultrasound sensors or a magnetic inductive sensor or an X-ray unit or amicrophone. In particular, in monitoring pressure development onstart-up of the pump, a slow rise in pressure may be evaluated as bindercontaining gas bubbles in the binder line.

The venting device is preferably fitted at local high points and pointswith volume flow changes, such as, for example, sharp-edged openings,pressure reducers, cross-section constrictions, at which air bubbles maycollect. Preferably a venting device with a switchable valve is combinedwith a venting device with a passive vent valve, wherein, on starting upthe apparatus, first the switchable valve is used to vent larger amountsof air, and during normal operation, venting is effected solely oroverwhelmingly by the passive vent valve.

The binder line may have one or more pressure control valves, which, aspressure switching valves, open from a predetermined switching pressureonwards and thereby release a binder feed at the spray nozzle(s), or, aspressure regulating valves, also open from a predetermined switchingpressure onwards and at the same time regulate a pressure on the outflowside of the pressure regulating valve to a predetermined pressure range.Such pressure control valves then have the additional function of apressure reducer. With one or more such pressure control valves, thebinder line may be divided into different pressure zones. These pressurecontrol valves preferably have different switching pressures. Inparticular, the pressure control valves are so arranged in the binderline that pressure zones are formed with pressure which reduces withdistance from the binder reservoir.

The several pressure control valves may be fitted in a main run of thebinder line, so that the main run is also divided into several pressurezones.

One or more pressure control valves may be provided in a branch run ofthe binder line branching off the main run, so that the respectivebranch run is closed if there is an undershoot of the switchingpressure. This avoids the main run becoming empty, and the respectivepressure control valve is assigned to one or more spray nozzles locatedin the branch run.

Due to the provision of one or more pressure control valves, pressurevariations in the binder line may be controlled and monitored in atargeted manner. Such pressure variations may be caused by heightdifferences along the binder line, long line lengths and a resultantdrop in pressure, temperature variations in the binder line, or pressurefluctuations due to switching processes. With the pressure controlvalves, emptying of the binder line, in particular the main run of thebinder line, may be prevented, so that a rapid start-up after a halt inoperations is possible since at least the main run of the binder line isalready filled with binder. In this way, pressure shocks are alsoavoided or reduced. The pressure control valves may also be integratedin spray nozzles or fitted in combination with them. Such spray nozzlesclose automatically below a predetermined closing pressure, so thatemptying of the binder line in the area of the spray nozzles is avoided.The spray nozzles are often located in branch runs. The pressure controlvalves close, preferably automatically, if a predetermined closingpressure is undershot, so that they may automatically isolate individualzones of the binder line. Such pressure control valves function asrun-out stops, to prevent emptying of the binder line.

To create zones with different pressure, pressure reducers may also beused instead of pressure control valves and are located in theappropriate lines.

Such pressure reducers may also be assigned to or integrated withindividual spray nozzles. Such a pressure reducer lowers the pressure toa predetermined reduced pressure level. By this means it is ensured thatthe binder is present at the spray nozzle with the constant reducedpressure so long as, in the area before the pressure reducer, the binderis present at an essentially desired but higher pressure. The pressurein the line may therefore fluctuate and nevertheless the binder ispresent at the spray nozzle concerned with a predetermined pressure, anda predetermined amount of binder plus a predetermined spray profile isoutput by the nozzle.

Such a pressure reducer may respectively be assigned to an individualspray nozzle or to a group of several spray nozzles.

The binder line is preferably designed with an elasticity for theelastic buffering of binder with an elasticity volume of 1 per mille andpreferably at least 1% of the total volume of the binder line on thebasis of pipe wall elasticity and/or at least one gas pocket and/or apressure vessel with gas cushion. Preferably this elasticity volume isat least 2% or at least 5% of the total volume of the binder line. Onaccount of this elasticity, pressure fluctuations in the binder line maybe balanced out without generating pressure shocks, or the effects ofpressure shocks may be reduced. In order to provide pipe wallelasticity, plastic pipes, in particular PE pipes, made in particular offlexible polyethylene, are used for binder line. The inside diameter ofthe pipes amounts preferably to at least 16 mm. The binder line haspreferably a length of at least 100 m. It may be several kilometerslong. The binder line is preferably divided by the above-mentionedpressure control valves into zones or sections with a length of 100 m to600 m, preferably 250 to 500 m. Such zones of flexible pipes offersufficient elasticity to dampen pressure peaks occurring on the closureof shut-off devices, which include valves and nozzles, in such a waythat they cause no damage. The PE pipes may also be made of rigidpolyethylene. In pipes of flexible polyethylene, it is easy to punchholes for nozzles or branch lines.

Preferably the maximum elasticity of the binder line is 10% and inparticular a maximum of 5% of the total volume of the binder line. Toomuch elasticity causes inertia in response behavior and may result in itnot being possible to deliver the binder in short pulses in a targetedmanner.

The binder line may have a main run in which a pressure reducer islocated, with a secondary run parallel to the main run and in whichthere is a non-return valve which opens against the flow direction ofthe pressure reducer. Depending on the principle of design, a pressurereducer also acts as non-return valve, so that a pressure peak whichoccurs on the pressure-reduced side of the pressure reducer cannotescape from the pressure-reduced zone due to the pressure reducer.Through the provision of the secondary run with non-return valve, whichopens against the direction of flow of the pressure reducer, such apressure peak may escape from the pressure-reduced zone through thesecondary run, so that here again the pressure reduced by the pressurereducer may cease. The secondary run preferably has a smaller diameterthan the main run.

Preferably the binder line has flexible branch lines which are connectedto a common line run or line section, wherein, at the end of the branchlines furthest away from the line section or line run, in each case aspray nozzle is provided. Owing to the weight of the spray nozzle or anadditional weight provided on it, the relevant branch line automaticallyaligns itself vertically. In this way the flexible branch line positionsand adjusts itself even when the whole dust binding apparatus is movedon account of external factors such as, for example, wind. Such a dustbinding apparatus may be designed both for producing artificial fog andalso for wetting the ground.

According to a third aspect of the present invention, the binder linemay be suspended from a bearer cable and the binder line made flexible,wherein the binder line is arranged roughly parallel to the bearercable, to which it is fastened at several points.

The binder line, with or without flexible branch lines, may be fastenedsuspended from a cable with suitable pipeline hooks. Such an arrangementmay be installed very easily and quickly over long sections. For thispurpose a thin bearer cable is adequate, in particular a steel cablewhich is stretched over a certain distance and from which the binderline is suspended by means of the pipeline hooks. Preferably the binderline is made of a plastic material, in which holes may be punched forconnection of the branch lines. This punching of the holes is alsopossible after suspension of the binder line from the bearer cable.

The spray nozzles may be arranged along the binder line at intervals ofno more than 10 m, preferably no more than 8 m and in particular no morethan 7 m.

The spray nozzles for spraying out the binder may be designed with acircular or circular-segment-shaped spray cone, with the maximumdistance between two adjacent spray nozzles not exceeding 80% of thediameter of this circle.

The binder line may be provided with at least one filling rate controlvalve, which, with the aid of a detected volumetric flow of the bindermedium, opens a passage for the binder in roughly inverse proportion tothe volumetric flow; this means that the lower the volumetric flow, themore the filling rate control valve is opened. With a low volumetricflow, the passage is completely opened. With a high volumetric flow, itmay be completely closed or closed to the extent that a previouslydetermined volumetric flow is not exceeded. By this means it is ensuredthat a pump is not operated outside its QH characteristic (=volumetricflow-height characteristic). It may also be ensured by this means that,on refilling a binder line, the volumetric flow is initially limited sothat, while expelling the air present in the binder line, no excessivepulses build up which, at the end of the refilling process, would causea correspondingly high pressure shock; the slow filling is therefore anadditional function of this valve.

The volumetric flow may be determined with the aid of the pressuredifference in the direction of flow before and after the filling ratecontrol valve and/or the filling rate control valve may additionally becontrolled by a control unit, wherein the desired volumetric flow may beset.

The binder line may be provided with at least one filling control valve,which, with the aid of a detected filling state of the binder line,opens a passage roughly proportional to the filling state. This fillingcontrol valve acts in a similar manner to the filling rate control valvedescribed above and prevents too high a volumetric flow on refilling,which would cause a high pressure shock at the end of the refillingprocess.

The filling control valve may be designed with two opening stages,wherein, if the filling level is low the passage is opened onlyslightly, and with a high filling level the passage is openedcompletely. The filling control valve may also be opened or closedcontinuously.

The binder line may have a pressure retention valve, which, with the aidof a pressure detected in the binder line in the flow direction beforethe pressure retention valve, opens roughly in proportion to thepressure. By this means, the pressure in the flow direction before thepressure retention valve is held roughly constant, since, if there is areduction in the detected pressure, the pressure retention valve closesslightly so that, due to the backup, the pressure in the flow directionbefore the pressure retention valve rises again. The pressure retentionvalve is preferably located in a main run of the binder line.

The binder line has a main run and a branch run which branches off fromthe main run. A control valve is provided in the branch run.

The control valve may be in the form of a pressure relief valve whichopens roughly in proportion to the pressure in the main run. If thepressure in the main run rises above a predetermined pressure, thisleads to diversion of the binder over the branch run. The binder may bedischarged via spray nozzles or over an empty line. In this way it isensured that there is no undesired high pressure in the main run. Thepressure relief valve may open only after a predetermined minimumpressure is reached in the main run.

The control valve in the branch run may also be in the form of a quickdrain valve, which, after a predetermined minimum pressure is reached inthe main run, substantially opens fully, so that a rapid rise inpressure in the main run may be counteracted. After the pressure in themain run has fallen, the quick drain valve is able to close more slowlythan it opened, so that a slow build-up of pressure in the main run isonce more possible.

The binder line may be connected to a well pipe which leads downwardsfrom the binder line into the underground well. A pump is fitted in thewell pipe, and the control valve in the branch run is so controlledthat, when the pump is switched on, the control valve is graduallyclosed over a predetermined interval of time and/or is gradually openedover a further predetermined interval of time when the pump is switchedoff. In the case of such well pipes, binder and water respectively aredelivered in large quantities. The pump is generally fitted deepunderground, resulting in the formation of a high water column. The riskof pressure shocks is high. Through the gradual closing of the controlvalve when the pump is switched on, the channeling of the binder throughthe branch line is gradually reduced, by which means the pressure in thebinder line is gradually increased. On switching off the pump, thecontrol valve is gradually opened, so that the pressure in the binderline is gradually reduced and a pressure shock is prevented. The openingof the control valve preferably takes place shortly before the pump isswitched off so that, when the pump is switched off, there is alreadyreduced pressure in the binder line.

The binder line may have a control valve which is controlled by acontrol device in such a way that it opens slowly over a predeterminedinterval of time with the switching-on of the pump and/or is closed whenthe pump is switched off. With this control valve, pressure shocks whenthe pump is switched on and off are reduced. The control valve may be inthe form of a non-return valve which prevents a flow back into orthrough the pump.

The control device of the control valve may also be designed to controlthe pump, so that switching-on and off of the pump is effectedsynchronously with switching of the valve.

Preferably a control device is provided, which, depending on the fillingstate of the binder line, the filling level of the pressure vessel withgas cushion and/or the volumetric flow in the binder line, controls thesupply of binder from the pressure vessel with gas cushion into thebinder line. This control device is preferably so designed that, with alow state of filling of the binder line, binder is withdrawn from thepressure vessel with gas cushion at a high volumetric flow rate, inorder to fill the binder line as quickly as possible, while on reachinga higher filling state the flow of binder is reduced or stopped, so asto avoid a pressure shock. Initially, binder may be fed to the binderline by the pressure vessel with gas cushion and the pump actingtogether. As the filling state increases, the supply from the pressurevessel with gas cushion is reduced or stopped completely, and thedelivery rate of the pump is suitably adjusted and preferably reduced.

The filling state of the pressure vessel with gas cushion may bedetermined from the gas pressure, the binder pressure, by means of anultrasonic sensor or a volumetric flow measurement. The volumetric flowmeasurement may be made using a flow meter as described above. Severalpressure vessels with gas cushion may also be provided.

In the binder line it is possible to provide one or more cyclone filterswith a flush inflow line and a flush outflow line with a flush outflowvalve so that, when a binder flow is stopped by the cyclone filter, itis possible to flush the cyclone filter without having to drain theother central areas of the binder line. A pressure vessel with gascushion and/or an external water pressure port may be connected to theflush inflow line. The cyclone filter may then be installed in a suctionline and flushed during operation of the pump. The suction line is aline section located before a pump in the direction of flow. With thefitting of a filter in the suction line it is ensured that the binder isfiltered before it reaches the pump. By this means the operating life ofthe pump may be extended. To flush the cyclone filter, either the pumpis stopped and flushing medium is fed through the flush inflow line fromthe pressure vessel or from the external water pressure port or, toflush in the case of suction-side installation of the cyclone filter,the binder flow through the cyclone filter is stopped and the cyclonefilter is back-flushed.

With conventional apparatus for the avoidance of dust, large amounts ofwater are discharged locally, and then distributed by vehicles over awide area. Such distribution is often essential, in the case of knownsystems, for the success of dust avoidance. With the invention, on theother hand, binder may be evenly and automatically distributed overlarge areas. Provision for distribution e.g. by vehicles is hereunnecessary, since the invention is self-distributing in operation orhas a self-distribution system.

The dust binding apparatus systems described above may be used for thebinding of dust, wherein the individual aspects may be appliedseparately or in combination.

Such a dust binding apparatus may be used to generate artificial fog, inwhich case the dust is bound in the air.

A dust binding apparatus may also be used for wetting the ground, inwhich case the dust is bound on the ground and can no longer be swirledup into the air.

In such a method for the binding of dust, the binder is preferablydelivered at intervals with spraying phases and pause phases.

For wetting the ground, the spraying phases and the pause phases are atleast 2 minutes or 5 minutes, preferably at least 10 minutes. Thespraying phases preferably last no longer than one hour and inparticular no longer than 30 minutes. The pause phases may last forroughly the same length of time as the spraying phases. The pause phasesmay however also be longer and in particular a multiple of the sprayingphases.

In creating an artificial fog, the duration of the spraying phases andthe pause phases should preferably be no longer than 120 seconds and inparticular no more than 30 seconds. The duration of the spraying phasesand the pause phases may be a few seconds. For creating an artificialfog the spraying phases are preferably longer than the pause phases. Thepause phases are made short enough that no or only very small gaps occurbetween consecutive clouds of fog. The slower the airflow in which theartificial fog or clouds of artificial fog exist, the longer the pausephases can be. The larger the fog droplets are, the faster they sink sothat the corresponding pause phases may be made shorter. With a dropletsize of around 100 μm to 200 μm, the pause phases are preferably nolonger than 5 seconds. In a fog in which the droplets overwhelminglyhave a size of less than 100 μm, the pause phases may also be set to belonger. If it is desired to use as little binder as possible, e.g. toavoid water-logging the ground, it is also possible to make the sprayingphases as short as possible and to extend the pause phases. This must bedetermined empirically.

With the dust binding apparatus systems described above it is evenpossible to set and to operate very short pause phases of 1 to 3seconds. For such a rapidly switching interval operation the measuresexplained above, such as flexible storage capacity in a pressure vesselor in flexible lines and/or the provision of pressure control valves inor close to the spray nozzles, are of benefit, since by this means, evenwith a run with a length of at least 50 meters and in particular atleast 200 meters, such interval operation is possible.

For creating an artificial fog, the spraying phase is preferably longerthan the pause phase. The spraying phase may in particular be twice aslong as the pause phase or a multiple thereof.

To avoid the formation of puddles, the dust binding apparatus is sooperated that the binder is applied at a rate of no more than 6 l/m²hand preferably no more than 4 l/m²h and preferably no more than 3 l/m²h.If the binder is sealed, then these spraying rates are even lower,amounting preferably to no more than 1.2 l/m²h or no more than 1 l/m²hand preferably no more than 0.8 l/m²h.

The dust binding apparatus for the creation of an artificial fog ispreferably so operated that the binder is sprayed in an area which is sofar from the dust source that, in this area, the airflow is no greaterthan 1 m/s, in particular no greater than 0.8 m/s and preferably doesnot exceed 0.7 m/s. It is especially advantageous when the airflow is nogreater than 0.5 m/s.

The invention is explained below by way of example with the aid of theappended drawings, which show schematically in:

FIG. 1 an open-cast working with an apparatus for the binder of dust, ina plan view

FIG. 2 a line plan of the apparatus for the binding of dust of FIG. 1

FIG. 3 a standing arrangement of spray nozzles in a side view

FIG. 4 a spraying area of the nozzles of FIG. 3

FIG. 5 spray nozzles on a suspended pipeline in a schematic roughlysimplified perspective view

FIG. 6 a spraying area of the nozzles of FIG. 5 in a schematic plan view

FIG. 7 an apparatus to create a fog wall, in a schematic side view

FIG. 8 a cable arrangement for the mounting of a suspended pipelinesystem

FIG. 9 a further cable arrangement for the mounting of a suspendedpipeline system

FIG. 10 line plan of a further apparatus for the binding of dust

FIG. 11 a volumetric flow measurement in the secondary run

FIG. 12 a secondary run with non-return valve for the relief of pressurezones, and

FIG. 13 a detail of an apparatus for the binding of dust with a wellpipe.

The apparatus according to the invention is used for the binding ofdusts of a wide variety of origin, in particular mineral dusts, plasticdusts, wood dusts, also air impurities, by means of precisely appliedbinders. “Dust”, for the purposes of the present invention, covers allsolid and liquid particles in an atmosphere which can be removed fromthe atmosphere by a binder or which may be bound by a binder on theground, so that they do not return to the atmosphere. As well as solidparticles, dust may also include aerosols or vapors.

The binder is preferably water. The water is used generally withoutfurther additives, in particular without wetting agents. Only in winteroperation may it be expedient to add anti-freeze. The water may be drawnfrom various sources, for example, wells, drinking water pipes, cisternsor the like. If the water contains impurities, then it is expedient toprovide a filter. The pore size of the filter should not exceed 200 μm,and preferably should not exceed 150 μm. It may also be expedient to usefilters with a pore size of 130 μm.

A first embodiment of a dust binding apparatus 1 for an open-castworking is shown in FIG. 1. The open-cast working may be a gravelworking for the extraction of gravel or a stone quarry for the quarryingof stone. In the present embodiment, the open-cast working is a gravelworking. The gravel working has an unpaved roadway 2 which leads over aramp 3 into a gravel pit 4.

This gravel pit 4 has a screening unit 5 and a conveyor belt run 6. Theconveyor belt run 6 extends from a feed hopper 7, which is located inthe gravel pit 4, to a processing shed 8 which is located outside thegravel pit 4. The conveyor belt run 6 is made up of several conveyorbelts, wherein two adjacent conveyor belts form a transfer point 9 atwhich the gravel to be conveyed falls from one conveyor belt ontoanother conveyor belt.

The screening unit 5, the feed hopper 7 and the transfer point 9 of theconveyor belt run 6 form large sources of dust. In gravel pits andquarries, all locations at which gravel or stone is moved and poured ordumped are potentially intensive dust sources. Other dust sources are,for example, stone-crushers, silos and gravel or stone heaps onto whichconveyor belts discharge, together with handling areas.

In addition, dust is swirled up by vehicles moving along the ramp 3 andthe roadway 2.

Whether or not a certain area is to be rated as a dust source, at whichdust must be bound, also depends on the requirements for dust purity setby the adjacent neighborhood. In the case of the gravel working shown inFIG. 1 agricultural areas, for example meadows or fields, border thelower edge and right-hand edge of the gravel working in FIG. 1. Suchagricultural areas set high requirements for dust purity, since grass orcrops contaminated by dust are impaired in quality and considerablyreduced in value. In the case of the gravel working shown in FIG. 1,industrial areas with only limited sensitivity to dust border the upperand left-hand edge.

In order to satisfy these different requirements for dust formation anddust sensitivity, the dust binding apparatus 1 includes a wetting device10 for wetting the roadway 2 and the ramp 3 with binder, several localfog screen units 11 and two fog walls 12.

The fog screen units 11 are provided for screening the local dustsources in the gravel pit 4. The fog walls 12 are located in FIG. 1 atthe bottom and right-hand edge of the gravel pit 4, to prevent thetransfer of dust from the gravel pit 4 to the adjacent agriculturalareas.

The wetting device 10 has pipe sections 13/1 and 13/2 running next tothe roadway 2 on both sides. These pipe sections 13/1 and 13/2 are rigidpipes 13 (FIG. 3) laid on the ground, from which at regular intervals(e.g. every 5 to 10 m, preferably every 6 to 8 m) there branches off astandpipe 14 running vertically upwards. The standpipes 14 have in eachcase a length of 0.5 to 2 m. At the upper free end of each standpipe 14is a spray nozzle 15. Provided on the standpipe 14, adjacent to thespray nozzle 15, is a manually operable shut-off valve, in particular aball valve, by which the water supply to each individual spray nozzle 15may be switched on or off separately.

Preferably the spray nozzles 15 are in the form of pressure nozzles,which only open automatically from a predetermined opening pressureupwards, and close automatically below a predetermined closing pressure.By this means it is ensured that, on the one hand, binder is dischargedonly when there is an adequate pressure for spraying at the spray nozzle15. Moreover, the automatic closing of the spray nozzles 15 ensures thatthe standpipe 14 and the pipe section 13 do not empty when the wettingdevice 10 is not in operation. In this way, refilling of the pipesections 13 and the standpipes 14 is avoided, by which means on the onehand the risk of pressure shocks may be considerably reduced, and on theother hand operation may be allowed without significant delay. Inaddition, any unevenness in binder discharge, which might result frompartial or complete emptying of the line, is avoided by this means. Thespray nozzles 15 are so designed that the binder is sprayed with adroplet size corresponding to a fine spray mist. The droplet size issubject to a certain distribution, wherein the overwhelming number ofdroplets have a droplet size of at least 100 μm, preferably at least 150μm or at least 200 μm. They create a fine spray mist which can bedistributed evenly over a predetermined area (FIG. 1) in a semi-circleor a circle or a circle segment (e.g. a circle segment with 90° or 125°)or with an angular shape.

The amount of binder evaporated during spraying is low. The droplets maybe sprayed by the spray nozzle 15 to a distance of around 5 to 12 m. Thespray nozzles 15 are designed with a semi-circular spray pattern and soarranged that, with this spray pattern, they cover the adjacent roadway2 (FIG. 4). For wetting a roughly 5 m wide strip over a section lengthof 100 m, around 2 to 4 m³ binder are discharged. For this, theoperating pressure at the nozzle is around 2.5 to 4.5 bar, in order toensure a reliable dispersion of the spray mist. In practice it has beenfound that interval operation with a spraying time of around 5 to 15minutes and a pause of around 5 to 30 minutes, wherein the pause shouldbe at least as long as the spraying time, leads to efficient wetting.The pause times are adapted, preferably automatically, to the weatherconditions. The hotter and drier the ambient air, or the more wind ispresent, the shorter the pauses should be made.

Control of the spraying time for wetting the ground may also be effectedon the basis of the subsoil. Sealed ground such as e.g. an asphaltsurface, may absorb no significant amount of binder. For sealed ground,therefore, interval operation with a spraying time of around 5 to 15minutes and a pause of around 5 to 30 minutes, without intensivepre-wetting, is preferred.

If the ground, on the other hand, is not sealed, then it generally has aporosity which can store binder and release the stored amount of binder.The ground then forms a binder reservoir similar to a sponge. Forunsealed ground, preferably intensive pre-wetting is first carried out,lasting at least 30 minutes, preferably at least 45 minutes, and inparticular at least 1 hour, with binder being released at a rate of 1 to3 l/m². Thereafter, interval operation with short spraying times ofaround 2.5 to 10 minutes at a rate of 1 to 3 l/m² and pauses of around 5to 30 minutes may be implemented, in order to replace binder released bythe ground.

The control of spraying times is carried out preferably automatically bymeans of a central control unit. The central control unit may setspraying times automatically on the basis of predetermined weatherparameters (amount of precipitation, temperature, wind speed, airhumidity, intensity of solar radiation). The weather parameters may besupplied by suitable weather sensors (thermometers, wind gauges, raingauges) or by weather data obtainable from the internet.

In addition to the above-mentioned weather parameters, soil moisture mayalso be measured and taken into account in the control of spraying time.Allowance for soil moisture is especially expedient for dust bindingapparatus systems which wet the ground with binder to avoid dust. Thesedust binding apparatus systems are used in particular for porous ground,on which dust may be swirled up. Depending on their porosity, thesetypes of ground have varying capacity for the absorption of water.Accordingly, the thresholds for soil moisture are to be determined andset empirically. The measurement of soil moisture may also be expedientfor fog-creating dust binding apparatus systems. Here above all ameasurement of soil moisture is used to determine whether too muchmoisture is reaching the ground, with a risk of forming puddles.

The aforementioned weather parameters and/or soil moisture arepreferably combined in such a way that they are a criterion forevaporation. The greater the evaporation, the longer the automaticoverlap spraying times will be regulated or the more frequently sprayingwill take place. The evaporation rate may be represented for example bythe combination of atmospheric humidity, wind velocity, temperature andintensity of solar radiation. The regulation of spraying times is madepreferably in such a way that as far as possible exactly the amount ofevaporated moisture is replaced.

Such a control unit serves to ensure adequate dust binding, while on theother hand keeping the demand for binder, in particular the need forwater, as low as possible. This control unit is shown here for anembodiment for wetting the ground with binder. Such a control unit mayequally be used for binding dust by means of artificial fog.

The maximum length of any such wetting apparatus is around 500 m. Iflonger stretches need to be wetted, then several such wetting units maybe provided consecutively.

Provided along the ramp 3 is a suspended wetting device 10/2. Thesuspended wetting device 10/2 comprises a thin bearer cable 16, which isa steel cable, a pipeline 17, pipeline hooks 18, by which the pipeline17 is suspended from the bearer cable 16, flexible branch lines 19 andspray nozzles 20. The spray nozzles 20 are of similar design to thespray nozzles 15. They have however a full-circle spray pattern, so thatthe wetting device 10/2 may be positioned centrally over the ramp 3 andthe ramp is completely or almost completely covered by the spraypattern. Around every 5 to 7 m, a flexible branch line 19 with a spraynozzle 20 is provided along the pipeline 17. Adjacent to the spraynozzle 20 on the flexible branch line 19 is a stabilizer 52, whichencompasses the branch line 19 and, on account of its weight, ensuresthat the flexible branch line 19 hangs downwards and is alignedvertically, at least with its bottom section. By this means, theflexible branch line 19 positions and adjusts itself automatically, evenif the whole wetting device 10/2 is moved due to external circumstances,for example wind. The spray nozzles 20 are preferably once again in theform of pressure nozzles, which open after a predetermined openingpressure is reached and close automatically after a predeterminedclosing pressure. The opening pressure lies in the range of 1.5 to 4bar. The closing pressure is in each case somewhat lower. The maximumlength of the wetting device 10/2 is around 500 m. The wetting device10/2 is preferably operated at intervals of 10 to 15 minutes, with pausetimes of 10 to 30 minutes. The wetting device 10/2 is preferablyarranged at a height of at least 5 to 6 m above the ground. The pipeline17 is preferably made from plastic pipe, in particular polyethylenepipe. It has an inside pipe diameter of for example 16 to 40 mm.

The fog screen units 11 are in principle formed in exactly the same wayas the suspended wetting device 10/2, with a bearer cable 16, a pipeline17, pipeline hooks 18, flexible branch line 19 and spray nozzles 21(FIG. 5). The spray nozzles 21 of the fog screen units 11 differ fromthe spray nozzles 20 of the wetting device 10 in that they spray thebinder much more finely, i.e. with a droplet size of 30 to 120 μm, inparticular 60 to 90 μm. Such fine droplets form a fog, which settlesgradually on the ground. Such fine droplets cannot be sprayed so far asthe larger droplets of the wetting device 10 described above. Themaximum range here is around 1.5.m and generally lies between 0.8 and1.3 m. The spray nozzles 21 with their flexible branch lines 19 arearranged on the pipeline 17 at intervals of 0.7 to 1.5 m, in particularintervals of 0.9 to 1.2 m. To provide an especially dense fog it mayalso be expedient to arrange two fog screen units 11 next to one anotherin parallel, with the pipelines 17 arranged at a distance of 1 to 2 mapart. The nozzles of the two fog screen units 11 are then preferablyarranged offset to one another in the axial direction.

The pipeline 17 is preferably made of flexible plastic, e.g. flexiblepolyethylene. Holes may be punched in such a pipeline 17 in order toconnect the branch lines 19. This may also take place after completeinstallation of the system, by which means it is also possible toprovide locally, as required, several spray nozzles 20 on a line. If anespecially dense fog is required locally then the spacing of the spraynozzles may be reduced to 0.5 m or 0.25 m or even to 0.1 m. Equally itis possible to remove subsequently spray nozzles 21 or a branch line 19with the corresponding spray nozzles 21, and to close the relevantopening with a plug. In this way, subsequent changes may be made to thesystem. This is especially advantageous in cases where, owing to changedcircumstances, a different requirement for fog has arisen. Such changesare always possible when the pipeline is made of a plastic in which itis possible to stamp or punch the relevant holes. This applies equallyto a suspended and to a ground-based system in which the relevantpipeline is laid on the ground.

The use of flexible plastic pipes for the pipeline 17 also has thefollowing advantages:

-   -   Due to the elasticity of the plastic pipes, extensions in length        may be absorbed easily. Consequently, these systems may be        installed and operated simply over long stretches from 500 m up        to 5 km. In the case of steel pipes there would be the danger        that, on account of temperature fluctuations, longer extension        might occur, leading to leaks at the joints.    -   The plastic pipes are weatherproof. In the event of a storm,        they yield elastically, returning to their original position        after the storm.    -   With a suspended system, mounting on the steel bearer cable 16        is very easy, by fixing the pipeline 17 using the pipeline hooks        18. For permanent mounting of the pipeline 17, a steel cable        with a diameter of 5 to 8 mm is sufficient, supports for        tensioning the steel cable may be provided at intervals of 50 to        150 m, so that large areas may be spanned and the supports do        not interfere with operations beneath them.    -   The apparatus may be variably enhanced by extra nozzles, or        nozzles may be subsequently removed.

The operating pressure is around 3 to 6 bar. The higher the operatingpressure, the finer are the droplets and therefore the better theability of the fog to float in the air, although there is also a greatersusceptibility to the effects of wind. Here too it is possible to usethe aforementioned pressure nozzles with predetermined opening andclosing pressure.

Such a fog screen unit 11 may be used in continuous operation. It may,however, also be expedient to operate such a fog screen unit with veryshort pulses of 1 second to 120 seconds and corresponding short pausesof 1 second to 120 seconds since, due to the floating ability of thefog, even with such pulsed operation, a permanent fog wall may beprovided. With such a pulsed operation, consumption of binder may beconsiderably reduced, without impairing the efficacy of dust binding.This kind of pulsed operation is especially advantageous at locationswith no or only very limited airflow.

The fog walls 12 are formed just like the fog screen units 11 butcomprise one or more parallel pipelines, which extend over longerdistances and are provided throughout with spray nozzles 21 at regularintervals. The pipelines 17 may also be arranged lying vertically oneabove the other (FIG. 7), so that a fog wall with a height of severalmeters is formed. In the embodiment shown in FIG. 7, seven pipelines 17are arranged one above the other, in each case with a spacing of 1 m, sothat a fog wall with a height of seven meters is formed.

Both the fog screen unit 11 and also the fog wall 12 are so arrangedrelative to a dust source that the fog is created not at the dust sourcebut instead at a short distance from the dust source. At the point oforigin of the dust there is generally a strong airflow, which swirls upthe dust. Supplying such a dust origin point with fog would only lead tothe fog being moved away from this point by the airflow, and a largeportion of the binder would have no effect. The fog is thereforeprovided at a point adjacent to the point of dust origin, where the airis calmer. Here the dust may be bound much more efficiently. The airflowis preferably limited to a maximum of 1 m/s, in particular 0.8 m/s or0.7 m/s and preferably to a maximum of 0.5 m/s. The distance between thearea in which the artificial fog is provided and the point of origin ofthe dust is therefore chosen so that this limit value is maintained.

The fog screen units 11 are preferably so designed that, as far aspossible, they completely surround the dust source. If the dust sourceis already screened off by a physical wall, then it may also beexpedient to design the fog screen so that its ends are flush with thiswall, so that together with the wall the dust source is surrounded, andin particular the movement of the dust along the wall and beyond it isprevented. The fog screen unit thus forms a wall termination.

The fog wall 12 preferably has a gutter 22 to collect the fog droplets.The water collected in this way is fed to a tank 23 from which it ispumped back into the pipeline 17 of the fog wall by means of a pump 24.The binder is thus conveyed in a circuit. Provided at one point in thiscircuit is a filter 25, by which the dust particles are removed from thewater. Alternatively, of course, the water which has been used once maybe disposed of, in which case no filter need be provided.

The fog wall 12 preferably has a central binder source 26, which may befor example a well (FIG. 2). The binder is preferably pure water. Thewater is taken from the binder source 26 by means of a pump 27. Locatedin a line section 28 which extends from the binder source 26 to the pump27 are a manual shut-off valve 29 and a non-return valve 30 which, inthe event of a pump failure, prevent water from flowing back into thebinder source 26. At the outflow side of the pump 27, a main line 31leads to the wetting device 10, the fog screen units 11/1 and 11/2, andthe fog walls 12/1 and 12/2. From the main line 31 a main run branchesoff to the wetting device 10, the fog screen units 11/1 and 11/2, andthe fog walls 12/1 and 12/2. Provided at the main runs are switchingvalves 32/1 to 32/5 respectively, which may be operated individually bya central control unit 38. With the switching valves 32/1 to 32/5, thewater supply to the individual main runs may be switched on and off. Byactuating switching valve 32/1, interval operation with a spraying timeof around 5 to 15 minutes and a pause of 5 to 30 minutes may beinitiated at the wetting device 10, and by actuating switching valves32/2 to 32/5, short pulses of 1 second to 120 seconds with correspondingshort pauses of 1 second to 120 seconds may be initiated at the fogscreen units 11/1 and 11/2 and/or at the fog walls 12/1 and 12/2.

A wetting device 10 divides the main run into two sub-runs for the lyingwetting device 10/1 and the suspended wetting device 10/2. Located atthe start of each of the two branch runs is a pressure reducer 33/1,33/2, which reduces the pressure provided by the pump 27 to theoperating pressure of the respective wetting device 10/1 or 10/2. In themain runs of the fog screen units 11/1 and 11/2 and the fog walls 12/1and 12/2 there is also in each case a pressure reducer 33, which heretoo sets the operating pressure suitable for the respective spraynozzles 21. Instead of the pressure reducers, further pumps may also beprovided, which then generate a higher pressure especially for the fogscreen units 11/1 and 11/2, so that the operating pressure of the mainpump 27 may be lowered. This therefore involves a further, decentralizedbinder feed.

The wetting device 10, the individual fog screen units 11/1 and 11/2,and the individual fog walls 12/1 and 12/2 may be operated independentlyof one another. From the main run of the fog screen unit 11/1 therebranches off a branch run 34, by which the screening unit 5 issurrounded. The spray nozzles 21 are here arranged at a predetermineddistance of 0.5 to 1.5 m from the screening unit 5, which forms a majordust source, so that a fog wall forms at this distance around the dustsource. In a corresponding manner, further branch lines 35, 36, 37 areprovided at the second fog screen unit 11/2, in order to surround thefeed hopper 7 and the transfer points 9 at a suitable distance.

The line section 28 may also be in the form of a well pipe (FIG. 13).The well pipe 28 extends through a vertical well bore 58 deep into theearth. Instead of the pump 27, a deep pump 59 is installed in the wellbore 58 and connected to the well pipe 28, in order to pump water fromthe well bore 58 into the dust binding apparatus 1. Provided in thesection of the line section above ground is a branch run 60, whichbranches off from the line section 28 and has a drain hole 61. Locatedin the branch run 60 is a control valve 62, which may be operated by acentral control unit.

Instead of the vertical well bore 58, a shaft or a concreted deep tankmay also be provided.

On switching on the pump 59, the control valve 62 is gradually closedover a predetermined time interval. In this way, the pump 59 builds up apressure in the line section 28 not suddenly but gradually, since tobegin with, a portion of the water and/or binder in the branch run 60escapes from the drain hole 61 through the control valve 62.

On switching off the pump, the control valve 62 is gradually opened,whereby the pressure in the line section 28 is gradually reduced,thereby counteracting a pressure shock. The opening of a control valvepreferably takes place shortly before switch-off of the pump so that, onswitching off the pump, there is already a reduced pressure in the linesection 28, thereby reducing the risk of a pressure shock. The controlvalve 62 may also be designed as an automatically opening pressurecontrol valve, which opens once a predetermined opening pressure isreached. This opening pressure is greater than the operating pressure.If there is a sudden failure of the pump 59, a pressure peak isgenerated in the line section 28 and is dissipated via the automaticallyopening pressure control valve 62. Due to reflection, severalconsecutive pressure peaks may occur and are diverted away one after theother via the branch run 60. It is also possible that this or anothervalve immediately opens suddenly on pump failure, on the one hand so asto divert pressurized binder, or to facilitate diversion for thefollowing pressure peak—it is therefore already open before occurrenceof the pressure peaks—consequently it is also not necessary for thesepeaks to be detected by the valve. It is also possible that this oranother valve allows an inflow of air or other media, so as tocounteract the risk of a cavitation shock.

In principle it is also possible to provide two separate branch runs,wherein, in one branch run a control valve operable by the centralcontrol unit and in the other branch run an automatically openingpressure control valve are provided. It is also possible to provide justa single branch run, in which the automatically opening pressure controlvalve is provided.

FIG. 8 shows masts with tension cables 56 for fixing the bearer cables16. The bearer cables may, however, also be fixed directly to any otherdesired elevation, e.g. a building 57 (FIG. 9).

FIG. 10 shows the line-routing plan of a second embodiment of the dustbinding apparatus 1. Parts identical to those of the first embodimentare given the same reference number and are designed exactly like thosein the first embodiment, so that a precise description of these partsmay be omitted.

This dust binding apparatus 1 again includes a binder source 26 orbinder reservoir, a pump 27 which delivers binder, in particular water,from the binder source 26 via a line section 28. Located in the linesection 28 are a manual shut-off valve 29 and a non-return valve 30.Also provided in the line section 28 is a filter 39. The filter may beprovided with a filter medium which has a pore size of 130 μm. It is,however, possible to provide a filter without filter medium, such as forexample a cyclone filter.

From the pump 27, a main line 31 leads to a wetting device and/or to afog screen unit or a fog wall. These facilities have in each case atleast one line run with one or more spray nozzles. These facilities aretherefore generally described below as nozzle run 40. The secondembodiment has two such nozzle runs 40, each beginning with a switchingvalve 32. Connected to the line 31 leading to the nozzle runs 40 is apressure vessel with gas cushion 41. From the line 31 to the pressurevessel with gas cushion 41 leads a thin feed line 42 and a thickdischarge line 43. Provided in the discharge line 43 is a non-returnvalve 44, which is so fitted that water from the pressure vessel withgas cushion 41 can flow only in the direction of the line 31 through thedischarge line 43.

If the pressure vessel with gas cushion 41 is filled with water, thenthis water flows solely through the thin feed line 42. On draining ofthe pressure vessel with gas cushion, the water can flow both throughthe discharge line 43 and also through the feed line 42 into the line31, and from there to the nozzle runs 40. The diameter of the dischargeline 43 is preferably at least twice and in particular four times aslarge as that of the feed line 42. It is however also possible that thefeed line 42 acts only as feed line, if it contains e.g. a restrictorelement with passage in only one direction.

Through the provision of the thin feed line 42 and the thick dischargeline 43, emptying of the pressure vessel with gas cushion may take placesignificantly more quickly than filling.

Provided in the line 31 is a switching valve 45 which is operated by thecentral control unit 38. The switching valve is fitted in the directionof flow after the pressure vessel with gas cushion 41. The switchingvalve 45 has several opening positions, so that by means of theswitching valve 45, different cross-sections may be set. The openingcross-section may be varied in several steps or also without steps.

Provided in the area between the switching valve 45 and the nozzle runs40 is a flow meter 46 which is connected to the central control unit 38and transmits to the latter the respective current volumetric flow. Afurther flow meter 48 is provided in at least one of the nozzle runs 40.

At the end of one of the nozzle runs 40 is a switching valve 47, whichmay be operated by the central control unit 38 to drain the nozzle run40.

Unless otherwise stated below, this dust binding apparatus 1 of thesecond embodiment functions in exactly the same way as that of the firstembodiment, in that water is sucked out of the binder source 26 by thepump 27, fed to the nozzle runs 40, and is there discharged via spraynozzles (not shown in FIG. 10) controlled by the switching valves 32.

The switching valve 47 at the end of one of the nozzle runs 40 has twofunctions. If this dust binding apparatus 1 is operated in winter then,if there is a danger of frost, the nozzle run 40 may be drained byopening the switching valve 47 so that air is allowed into the nozzlerun 40. The air may be provided from a compressed air source or by meansof a suitable pump. If the binder or the water has impurities, thesegenerally collect in the end section of the nozzle runs 40. Theseimpurities may be flushed out by opening the switching valve 47 andflushing the nozzle run 40 with water.

Both the draining of the nozzle run 40 and also the flushing of thenozzle run 40 are controlled by the central control unit 38.

The pressure vessel with gas cushion 41 may be a diaphragm vessel whichhas a diaphragm dividing the diaphragm vessel into a gas pressurechamber and a binder chamber. On filling of the pressure vessel with gascushion 41, the gas in the gas pressure chamber is compressed, whichraises the pressure in the pressure vessel with gas cushion 41. If oneor more of the nozzle runs 40 is drained, then they must be completelyrefilled before operation can be resumed. With the pressure vessel withgas cushion 41, a large volume of binder may be made available quickly.On account of the large cross-section which is available duringdischarge of the binder from the pressure vessel with gas cushionthrough the discharge line 43 and the feed line 42, the binder may beconveyed rapidly, i.e. with a high volumetric flow, to the nozzle runs40. A rapid movement of binder or water into the incompletely fillednozzle runs conceals the risk of a pressure shock, which occurs when thenozzle run concerned is completely filled. In this respect, use of thepressure vessel with gas cushion 41 is advantageous, since, on conveyingthe binder out of the pressure vessel with gas cushion the gas pressurechamber expands, causing the pressure in the pressure vessel with gascushion 41 to reduce, and to reduce further with increasing withdrawalfrom the pressure vessel. This means that, at the start, the binder isconveyed out of the pressure vessel 41 under high pressure towards thenozzle runs 40, wherein this pressure and with it the flow rate reduce.In this way the risk of a pressure shock is somewhat reduced. At thesame time, at the start of conveyance, a large amount of binder from thepressure vessel with gas cushion 41 is made available very quickly, sothat drained nozzle runs 40 may be rapidly refilled.

If the lines are flexible plastic lines, then these lines also form abinder buffer. When operation is started, firstly from the pressurevessel the “buffer” of the lines is filled, which counteracts pressureshock during rapid line filling. The combination of a pressure vesselwith gas cushion and flexible plastic lines is therefore especiallyadvantageous.

In operation, conditions occur very seldom in which the pressure vesselwith gas cushion is completely filled or completely empty. Instead, thepressure vessel with gas cushion is mostly partly filled and partlyempty, so that in operation it can compensate quickly and reliably forfluctuations in binder requirement, without the risk of pressure shocks.

The volumetric flow fed through the line 31 by the pump 27 and thepressure vessel with gas cushion 41 is measured by the flow meter 46.The control unit that detects this volumetric flow may, with the aid ofthis volumetric flow, set the pumping capacity of the pump 27 and/or theopening cross-section of the switching valve 45. If a maximumpermissible volumetric flow is exceeded, the pumping capacity of thepump 27 may be reduced, and/or the opening cross-section of theswitching valve 45 may be reduced, by which means both the volumetricflow from the pressure vessel with gas cushion 41 and also thevolumetric flow generated by the pump 27 may be controlled. Since thepressure vessel with gas cushion 41 is connected to the line 31 in thearea between the pump 27 and the switching valve 45, the pressure inthis line section may be so controlled by the pumping capacity of thepump 27 and the opening position of the switching valve 45 that waterflows into the pressure vessel with gas cushion 41 when the pressure inthis line section is greater than in the pressure vessel with gascushion 41, and water is withdrawn from the pressure vessel with gascushion 41 when the pressure in this line section is less than in thepressure vessel with gas cushion 41. In normal operation there is abalance between these two pressures, so that the filling state of thepressure vessel with gas cushion 41 remains constant. Due to the factthat the feed line 42 has a smaller cross-section, the volumetric flowon filling of the pressure vessel with gas cushion 41 is correspondinglylow so that, even with a slightly filled pressure vessel with gascushion 41 and with the nozzle runs 40 not yet completely filled, it ispossible to feed the major part of the volumetric flow conveyed by thepump 27 to the nozzle runs 40. If, however, the pressure vessel with gascushion 41 is filled with binder or water, then a large amount of watermay be fed rapidly to the nozzle runs 40 by opening the switching valve45.

Preferably, filling level sensors (not shown) are provided in the nozzleruns 40. The nozzle runs 40 may have a filling level sensor at each oftheir end sections. They may be distributed over their length, but alsohave several filling level sensors. The filling level sensors areconnected to the central control unit 38, so that the central controlunit 38 may detect the filling levels of the nozzle runs 40. The fillinglevels may be taken into account in controlling the opening position ofthe switching valve 45 and the pumping capacity of the pump 27, and thefuller the nozzle runs are filled with binder, the more the volumetricflow or the flow rate is reduced.

The flow meter 48 located in the nozzle run 40 is used to monitor thefunctioning of this nozzle run. If this nozzle run has, for example, aleak, then the volumetric flow in this nozzle run is increased. It isdetected by the flow meter 48. A fault report may be output, and at thesame time this nozzle run may be shut off by means of the relevantswitching valve 32. If on the other hand one or more spray nozzles areblocked, then the relevant volumetric flow is reduced. This can also bedetected by means of the flow meter 48 and a corresponding fault reportmay be output. The flow meter 48 located in one of the nozzle runs 40may also be used to detect volumetric flows which are too high and couldpresent a risk of pressure shock. Then, with the aid of this detectedvolumetric flow in one of the nozzle runs 40, the entire volumetric flowwhich is controlled by the switching valve 45 and the pumping capacityof the pump 27, is suitably reduced.

Preferably such flow meters 48 are provided in all nozzle runs 40, sothat all nozzle runs 40 may be monitored individually.

In addition, using the flow meters 46, 48, the volumetric flows in thedust binding apparatus 1 may be detected and recorded. By this means itis possible to check later whether or not the dust binding apparatus 1was operating correctly at a certain point in time.

The filling level sensors described above may also be in the form ofpressure switches, which output a signal only when a predeterminedpressure has been reached. By this means it is possible to detect notonly whether the nozzle runs 40 are filled with binder, but also thatthe filling at the site of the relevant pressure switch has a certainpressure. The switching threshold of this pressure switch should besomewhat less than the operating pressure of the spray nozzles in thenozzle runs 40. Suitable thresholds of the pressure switches liepreferably in the range from 1.5 bar to 3 bar.

With long nozzle runs 40 it may also be expedient, with increasingdistance from the binder source 26, to provide spray nozzles withincreasingly low operating pressure (opening pressure and closingpressure), since the pressure in the nozzle run 40 may reduce withincreasing distance. The individual spray nozzles therefore have a lowopening and closing pressure with increasing distance from the bindersource 26. The pressure threshold of the pressure switch in the vicinityof the relevant spray nozzles should be matched to the opening andclosing pressure of these spray nozzles.

By means of pressure reducers, cross-section restrictions because of areduction in line cross-section, or through the provision of suitablenarrow points, the nozzle runs 40 may also be set in pressure zones in atargeted manner. The pressure zones may be designed for example withreduced pressure with increasing distance from the binder source 26, sothat different but defined pressure conditions exist in the individualpressure zones. Through such pressure settings, discharge with very highuniformity may be obtained. The pressure at the respective nozzles maybe kept to a defined value permanently, regardless of whether it is thefirst, the last or any intermediate nozzle of a line. Preferably thenozzles are in the form of pressure nozzles with a predetermined openingand/or closing pressure, as described above.

The central control unit 38 may be designed so as to delay switching onand off of the pump 27. This is expedient in particular if the pumpingcapacity of the pump 27 is not gradually adjustable. Switching the pump27 on and off may cause cavitation problems in the pump or its assignedcomponents and may in each case create a pressure shock in the lines. Ifthe switch-off is delayed by a predetermined period of time, then it maybe that the operating conditions have changed again in the meantime, sothat the pump 27 should no longer be switched off. Such situations occurmainly when the control variables such as volumetric flow, filling leveland/or pressure in the line 31 or in the nozzle runs 40 in each case areclose to and fluctuate around the relevant thresholds. The dust bindingapparatus 1 is designed with a certain elasticity for flexible bufferingof binder so that, even when the thresholds are reached, it is stillpossible to continue operation of the pump 27, to convey a certainvolume further or, on the strength of the available elasticity, toprovide binder for the nozzle runs 40 without the pumping capacity ofthe pump 27. This elasticity is provided, for example, by the pressurevessel with gas cushion 41. In addition, such elasticity for theflexible buffering of binder may be provided by pipelines of a flexibleplastic material, in particular polyethylene, since this material isable to expand within certain capacity levels and can absorb binder byyielding flexibly. Through such time delay in switching the pump 27 onand off, combined with the flexible buffering of binder, the life of thepump 27 may be extended considerably. This is especially advantageouswhen the fog screen unit 11 described above or the fog wall 12 describedabove are operated with very short spray pulses. These pulses may becontrolled solely by switching of the switching valves 32, while thepump 27 may be operated continuously.

In the present embodiment, the time delay is realized in the centralcontrol unit 38. It is of course also possible to provide a separatetime delay element, in particular a time delay relay, which delaysswitching on or off of the pump 27 independently of the central controlunit 38.

It is also possible to provide in the main line 31 and/or in the nozzleruns 40 in each case one or more pressure sensors, which are linked tothe central control unit 38. The pressure values recorded by thepressure sensors may be used in a similar manner to the volumetric flowsdescribed above to control the volumetric flow in the main line 31 bymeans of the switching valve 45 and the pump 27. In this case, theswitching valve 45 and the pumping capacity of the pump 27 are switchedor changed when the measured pressure values exceed or fall belowpredetermined thresholds. Moreover, predetermined safety thresholds maybe provided which are greater than the thresholds for controlling normaloperation. If the pressure values measured by the pressure sensors reachthe safety thresholds, then this is evaluated by the central controlunit 38 as a safety problem, and the pump 27 is completely switched off,and/or safety valves (not shown) in the main line 31 and/or in thenozzle runs 40 are opened, so as to release binder to the outside, bywhich means the pressure in the dust binding apparatus 1 may be rapidlyreduced, and/or warning indications may be given.

In the embodiment explained above (FIG. 10), the pump 27 is locatedbetween the non-return valve 30 and the pressure vessel 41. In thecontext of the invention, the pump 27 may of course also be locatedunder water in the binder source 26.

Flow meters for measuring high volumetric flows are complex andexpensive. It is therefore expedient, in particular in areas of highvolumetric flows, to provide an auxiliary run 49 (FIG. 11) to a main run50, wherein the auxiliary run is a line with a smaller cross-sectionthan the line of the main run 50 and leads at both ends into the mainrun 50. The flow meter 51 which measures the volumetric flow through theauxiliary run 49 is located in that auxiliary run 49. Since thevolumetric flows through the 50 and the auxiliary run 49 are in acertain ratio, which corresponds to the ratio of the auxiliary run 49cross-section to the cross-section of the main run 50, the volumetricflow measured in the auxiliary run 49 may be used to reach a conclusionon the complete volumetric flow through the auxiliary run and the mainrun. Such an arrangement of the flow meter is advantageous in particularin the main line 31, since high volumetric flows occur here.

To ensure that a flow is actually present, an additional flow monitoringdevice may be provided in the main run 50 and indicates only whether aflow is present or not. Such a flow monitoring device may involve e.g.an impact disc flow meter. This may be used to determine whether or notthere is a flow in the main run, even if the auxiliary run is blocked.

It was explained above that the nozzle runs 40 may be divided bypressure reducers into separate pressure zones. Such pressure reducers53 generally act like a non-return valve and allow only a flow from theside with higher pressure to the side with lower pressure. If, however,short-term pressure peaks occur, they may gain access to the area withlower pressure or they may, for example, due to switching operations,occur directly in the low pressure area and no longer escape from there,since water cannot flow back through the pressure reducer 53. It maytherefore be the case that much higher pressures occur in pressure zonesthan the usual operating pressure in the respective pressure zone. Thiscan lead to damage.

If the line in which the pressure reducer 53 is located is provided withan auxiliary run 49 in which there is a non-return valve 54 which allowsa flow from the pressure-reduced side of the pressure reducer 53 to theside with higher pressure, the such pressure peaks are able to escapefrom the pressure zones (FIG. 12).

The central control unit 38 may be connected to sensors or onlineweather services, which detect the current weather conditions(temperature, atmospheric humidity, amounts of precipitation (forecastand already fallen), wind speed and direction, air humidity,evaporation) and control the discharge of binder accordingly. It mayalso be expedient for the control unit 38 to receive digital weatherinformation for the appropriate control of binder discharge. It has beenfound, for example, that at the end of a cool night or in the morning,it is sensible to wet the ground by means of a wetting device, since,with cool air, much less dust-containing water is evaporated than laterin the day when it is hotter. Such intensive wetting makes senseespecially on unsealed ground. If, however, the weather data show that,after a dry night, rain is expected soon, then intensive wetting shortlybefore the rain is superfluous. Such weather data is nowadays availablewith a high degree of precision and may be taken into account incontrolling the discharge of binder. By this means, the system capacitycan also be adapted to the weather conditions, e.g. by changing theamount of precipitation, by varying the wetting interval or also byswitching on or off one or more nozzles or nozzle runs. The amount ofbinder discharged (per unit of time, either the amount discharged ineach wetting operation or the cumulative output per day) may be variedand adjusted in a targeted manner.

The apparatus may also be provided with sensors which detect vehiclesand/or persons so that sections of the apparatus may be switched on oroff based on the output signals of these sensors. If, for example,vehicles or persons temporarily occupy an area to be sprayed or providedwith fog, then the binder supply may be temporarily switched offlocally, so that the vehicles or persons are not sprayed. These sensorsmay be optical sensors, in particular cameras, or induction coils letinto the ground to detect vehicles. The local switching on or off ofsections may be implemented, for example, with an apparatus in which thespray nozzles and/or specific pipe sections are provided with switchablevalves or separate pumps.

It is, however, also possible to provide sensors to detect groundmoisture, fog and/or dust creation. These sensors may be moisturesensors or optical sensors such as cameras. Relevant camera images maybe analyzed automatically using optical image processing to determinewhether the ground is moist, if there is fog in the atmosphere and/or ifthere is a dust cloud. These optical sensors may be combined withspecial lighting equipment which makes appropriate dust particlesreadily discernible. Based on these sensor signals, the intensity ofdust binding may be controlled, wherein locally different intensity ofdust binding may be set based on the sensor signals.

The operating conditions and/or the sensor signals are preferablyrecorded and saved. By this means it is possible on the one hand toconform operation of the apparatus and on the other hand to show dustconditions if sensors are present which record dust conditions.

Instead of automatic control, recommendation messages may also be outputto an operator at a suitable output facility (screen, loudspeaker), sothat the operator of the apparatus can initiate suitable dust binding.

Precipitation rates are explained below with the aid of examples of dustbinding apparatus according to the invention:

A dust binding apparatus with a standing arrangement of several spraynozzles 15 according to FIG. 3 is designed for wetting a roughlystrip-shaped area. The spray cones of these spray nozzles 15 aresemi-circular in shape (FIG. 4). The radius of the spray cones is 6.4 mand the operating pressure is 3.5 bar. An individual spray nozzle 15sprays an area of around 64 m² and consumes around 190 liters of binderor water per hour of continuous operation. With continuous operation,the ground is wetted with around 3 liters per square meter per hour. Inpulsed operation, consumption of binder per hour may be reduced toapprox. 50-70 liters per hour and per nozzle. The spray nozzles 15 arearranged roughly 7 m apart from one another.

A further embodiment of the spray nozzle 15 has a throwing range of 9 mwith an operating pressure of 3.5 bar. Otherwise this embodiment of thespray nozzle corresponds to the standing arrangement of spray nozzlesdescribed above according to FIGS. 3 and 4 and with semi-circular spraycones. The wetted area per nozzle is around 130 m² and the consumptionof binder or water amounts to around 470 liters per hour per nozzle.This results in a precipitation rate of roughly 3.6 liters per m² perhour in continuous operation.

Examples of running times for a dust binding apparatus according to thetwo embodiments described above with a standing arrangement of spraynozzles 15 (FIGS. 3 and 4) are explained below.

On sealed ground, such as asphalt or concrete the ground is wetted for 5to 10 minutes in cool weather conditions. In warmer weather, wettingtakes place for a period of 5 to 20 minutes, with the pause time beingfrom half an hour to around 1 hour. In hot weather (air temperature >20°C.), the wetting time is 5 to 20 minutes and the pause time is reducedto 10 to 20 minutes.

The stronger the wind, the longer the wetting times and therefore theshorter the pause times which are set.

Sealed ground is hardly able to store water. It therefore dries out veryquickly and requires regular wetting; otherwise drainage water willoccur.

Open natural surfaces such as gravel, crushed stone or sand may storewater in contrast to sealed ground.

In cool weather (temperature <13° C.), wetting may take place in themorning for 0.5 to 1.5 hours, with no further wetting for the rest ofthe day. In warm weather (13° C. <temperature <20° C.) wetting takesplace in the morning for 0.5 to 1.5 hours, while further wetting maythen be applied for periods of around 10 to 20 minutes, in each caseafter pauses of 0.5 to 4 hours. The pause time depends mainly on thestorage capacity of the ground concerned.

In hot weather (temperature >20° C.), wetting takes place in the morningfor 1 to 1.5 hours. Further wetting for periods of 20 to 45 minutes ismade with intermediate pauses of 30 to 60 minutes. On very hot and inparticular windy days, continuous operation may also be expedient.

The continuous wetting of the ground may lead to a noticeable loweringof the ambient temperature. This applies especially to sunlit gravelpits which are protected from the wind. Due to wetting, the ground iskept cool, which considerably reduces the radiation heat radiated fromthe ground.

Examples of ground-wetting dust binding apparatus units with suspendedspray nozzles 20, as shown in FIGS. 5 and 6, are explained below.

In a first embodiment, the throwing range is 4 meters, and the throwingcone forms a full circle. Operating pressure lies in the range of 2 to 3bar. The area wetted per spray nozzle 20 comes to around 50 m² andconsumption of binder amounts to approx. 70 liters per hour per nozzle.

This results in a precipitation rate of around 1.4 liters/m² incontinuous operation.

In a second embodiment, the throwing range is 4.8 meters, while thethrowing cone again forms a full circle. Operating pressure lies in therange of 1.5 to 4.5 bar. The wetted area amounts to around 72 m² andconsumption amounts to approx. 70 liters of binder per hour per spraynozzle. This results in a precipitation rate of around 0.97 liters perm² per hour in continuous operation.

Typical examples of running time for a dust binding apparatus with suchsuspended nozzles are explained below, wherein these examples of runningtime apply to both types of nozzle.

In the case of sealed ground, such as asphalt or concrete, the ground isinitially wetted in cool weather conditions (temperature <13° C.) for aperiod of 10 to 20 minutes. Fresh wetting takes place after a pause ofone to several hours. In warm weather (13° C.<temperature<20° C.),wetting takes place for 10 to 30 minutes, with the pause time betweenconsecutive wettings being from around half an hour to a whole hour. Thefurther wettings are again carried out over a period of around 10 to 30minutes.

In hot weather (temperature >20° C.), the ground is wetted for a periodof 10 to 30 minutes. Pause times amount to around 20 to 30 minutes. Thestronger the wind, the longer the wetting times and therefore theshorter the pause times that are set.

In the case of open natural surfaces such as gravel, crushed stone orsand, in cool weather (temperature <13° C.), wetting takes place in themorning for 1 to 1.5 hours, with no further wetting for the rest of theday. In warm weather (13° C. <temperature <20° C.), again wetting takesplace in the morning for 1 to 1.5 hours. After pauses of 0.5 to 4 hoursfurther wetting is effected for a period of 20 to 40 minutes. In hotweather (temperature >20° C.), wetting takes place in the morning for 1to 1.5 hours, with further wetting for periods of 30 to 40 minutes.Pauses between individual wettings amount to 30 to 60 minutes.

The stronger the wind, the longer are the set wetting times, and theshorter the pauses. On hot windy days, continuous operation of the dustbinding apparatus may also be expedient.

Such a dust binding apparatus with suspended nozzles may be formed by abinder line 17 with an inside diameter of 28 mm, with branch lines 19and spray nozzles 20 arranged at regular intervals (approx. 6 to 7meters). For a section of the dust binding apparatus with a length of350 m and 59 spray nozzles, consumption amounts to 70 liters of binderper hour per nozzle, and total consumption is around 4.13 m³/h. The pipevolume comes to 67 liters.

This corresponds to 1.6% of the total consumption per hour. Such a lowpipe volume can be refilled rapidly after a pause or standstill.Refilling may be effected using a conventional standard pump, withoutthe need for a pressure vessel or pressure valve, which serves asrun-out stop.

For a dust binding apparatus with standing arrangement of the spraynozzles, a pipe section, for example, with an inside diameter of 61.2 mmay be provided over a length of 500 m. The pipe volume is then around1470 liters. 72 spray nozzles are arranged every 7 m, each having aconsumption of 190 liters of binder per hour and per nozzle. Totalconsumption is therefore around 13.7 m³/h. The pipe volume thereforeamounts to around 10% of the total consumption per hour. This meansthat, with a complete emptying of the pipe volume, it takes around 6minutes for the pipe volume to be refilled with binder, when the binderis conveyed at a constant rate. The rapid filling of a large volumecauses a risk of pressure shocks, as already explained above. For such adust binding apparatus it is therefore expedient to provide a pressurevessel with gas cushion, with a usable volume corresponding roughly tothe pipe volume. Here, a pressure vessel with a usable volume of 1500liters would be expedient. Alternatively, or additionally, a specialpump may be provided, in particular a speed-controlled pump or a pumpwith especially high delivery rate, in order to convey the binderquickly. Alternatively, or additionally, self-closing pressure controlvalves or pressure nozzles, which prevent or delay run-out, may also beprovided.

The longer the dust binding apparatus units, the greater—as a rule—isthe inside diameter of the pipe section 13. For a line length of forexample 1.6 km it is sensible to provide a pipe (rigid PE) with aninside diameter of 130.8 mm. In this case, 189 spray nozzles (standingarrangement) are connected roughly every 8.5 m. Each has a consumptionof 470 liters per h and per nozzle, with total consumption coming toaround 88.8 m³/h. The pipe volume amounts to approx. 21 m³. Thiscorresponds to around 25% of the consumption of binder per hour. Withconstant delivery, refilling of a completely emptied pipe volume wouldtake around 15 minutes. Such a long delay is in principle unacceptable.It is therefore advisable, with such a large pipe volume, for run-out oremptying to be avoided or considerably delayed. This may be achieved bymeans of self-closing pressure control valves or pressure nozzles. Witha standing nozzle arrangement, however, this is not necessary so long asthe dust binding apparatus runs horizontally. In the case of dustbinding apparatus extending over a difference in height which is greaterthan the height of the standpipes 14, it is expedient to provide thelower-lying spray nozzles with an automatically opening pressure controlvalve or pressure nozzle. However, with longer periods of inactivity,partial draining is difficult to avoid completely. It is thereforeexpedient to provide, in pipelines of a dust binding apparatus 1 withsuch a large pipe volume, pressure vessels with gas cushion and/or flowrestrictor valves, so that on refilling, a predetermined maximumvelocity is not exceeded.

It may therefore be stated that, with low pipe volumes as compared withregular consumption (pipe volume <3% of binder consumption per hour), nospecial measures are required for refilling. For fairly large pipevolumes, on the other hand, suitable measures should be taken (e.g.pressure vessels, self-closing pressure control valves or pressurenozzles, special pumps). In the case of large pipe volumes (more than15% of the regular binder consumption per hour or in particular morethan 20% of the regular binder consumption per hour), then the run-outor draining of the pipeline should be avoided or considerably delayed.Suitable measures for this purpose are the provision of self-closingpressure control valves and pressure nozzles. For dust binding systemswith a standing arrangement, self-closing pressure control valves andpressure nozzles are not in themselves necessary if the dust bindingapparatus is arranged in a horizontal plane. However, this is veryseldom the case, since the dust binding systems according to theinvention generally extend over quite long distances. The use ofself-closing pressure control valves and pressure nozzles is, however,also advantageous since pressurized binder is then always available inthe binder line, so that rapid start-up is possible after a pause.

Examples of dust binding apparatus units for creating fog and withsuspended spray nozzles 21, as shown in FIGS. 5 and 6, will be explainedbelow.

There are individual fog nozzles and individual nozzles combined into agroup of four.

The fog emission range amounts to around 80 cm per nozzle, measuredhorizontally at the nozzle. By the time the fog has reached the ground,it has expanded to approx. 1.5 m.

The individual nozzle consumes, with an operating pressure of 4 bar,around 7.5 liters of binder per hour; the 4-nozzle version about 30liters per hour. With pulsed operation, this results in consumption ofaround 0.002 liters per second and 0.008 liters per second,respectively.

Such a dust binding apparatus may also be designed as a low-flow dustbinding apparatus.

The individual nozzle then consumes around 5.5 liters of binder per hourand the 4-nozzle version approx. 22 liters of binder per hour (0.0015l/sec and 0.006 l/sec respectively).

The individual nozzles are generally installed in the pipeline around 10cm apart, and the 4-nozzle units around 0.5 to 2 meters apart.

Since part of the fog evaporates, it is difficult to determine aprecipitation rate for a dust binding apparatus producing fog, sincethis depends heavily on the current climatic conditions.

Examples of running times are explained below:

Case 1: Dust Binding at a Stone Crusher Machine

When the stone crusher machine is stationary, dust binder is inactive.When the stone crusher machine is in operation, fog is producedcontinuously.

The stone crusher machine is provided on two sides with a fogging line,each being 3 metres long and arranged 1.7 metres from the stone crushermachine.

The nozzles are spaced 1 metre apart, with six spray nozzles beingprovided. Operating pressure is 5 bar. Water consumption comes to(6×34=) 204 liters per hour in continuous operation.

Case 2: Indoor Dust Binding

In a refuse sorting building, several dust binding lines are fixed tothe ceiling of the building, 2 meters apart, with spray nozzles (groupsof 4) fitted every 1.5 meters. A total of 350 dust binding nozzles areprovided, which, with an operating pressure of 5 bar, have a waterconsumption of 11,900 liters per hour in continuous operation.

A spray pulse of 2 seconds duration is generated every 28 seconds. Themist is emitted at the building ceiling and falls downwards.

Each pulse consumes 6.6 liters of binder. This results in an effectivebinder consumption of around 800 liters per hour. This is onlyone-fifteenth of the consumption in continuous operation.

Case 3: Construction Vehicle

A dust-generating construction vehicle produces continuous dusty airwhen operating by swirling up dust from the ground, which rises from theground and moves away.

Attached to the construction machine on two sides are spray nozzles at aheight of 1.5 meters above the ground. Altogether ten spray nozzles areattached, with an hourly consumption of 300 liters at an operatingpressure of 4 bar.

To save water in mobile operation, the misting system is operated on apulsed basis. In each case mist is emitted for 1 second, then there is apause for 4 seconds.

Each mist pulse leads to a consumption of 0.08 liters of binder. Foreach hour of pulsed operation, binder consumption is 60 liters.Consequently, only a fifth of the amount of binder is used as comparedwith continuous misting.

LIST OF REFERENCE NUMBERS

-   1 dust binding apparatus-   2 roadway-   3 ramp-   4 gravel pit-   5 screening unit-   6 conveyor belt run-   7 feed hopper-   8 processing shed-   9 transfer point-   10 wetting device-   11 fog screen unit-   12 fog wall-   13 pipe section-   14 standpipe-   15 spray nozzle-   16 bearer cable-   17 pipeline-   18 pipeline hook-   19 flexible branch line-   20 spray nozzle-   21 spray nozzle-   22 gutter-   23 tank-   24 pump-   25 filter-   26 binder source-   27 pump-   28 line section-   29 shut-off valve-   30 non-return valve-   31 line-   32 switching valve-   33 pressure reducer-   34 branch run-   35 branch run-   36 branch run-   37 branch run-   38 central control unit-   39 filter-   40 nozzle run-   41 pressure vessel with gas cushion-   42 feed line-   43 discharge line-   44 non-return valve-   45 switching valve-   46 flow meter-   47 switching valve-   48 flow meter-   49 auxiliary run-   50 main run-   51 flow meter-   52 stabiliser-   53 pressure reducer-   54 non-return valve-   55 mast-   56 tension cable-   57 building-   58 well bore-   59 deep pump-   60 branch run-   61 drain hole-   62 control valve

1. Apparatus for the binding of dust, comprising: a binder reservoir,which provides liquid binder which is under pressure, a binder linewhich is connected to the binder reservoir, wherein there is connectedto the binder line at least one spray nozzle which may be located in thevicinity of a dust source, and that the binder line has one or morepressure control valves which, as pressure switching valves, open from apredetermined switching pressure upwards and thus release a binder feedto the spray nozzle(s), or as pressure regulating valves also open froma predetermined switching pressure upwards and at the same time regulatea pressure on the outflow side of the pressure regulating valve to apredetermined pressure range, and that the binder reservoir includes atleast one pressure vessel with gas cushion, which is divided into a gaspressure chamber and a binder chamber, wherein the binder line has alength of at least 100 m along which several spray nozzles are arranged.2. Apparatus for the binding of dust according to claim 1 in whichground is wetted with spray mist, and wherein the apparatus is sodesigned that no more than 6 l/m²/h of binder is discharged onto theground during a spraying operation.
 3. Apparatus according to claim 1,wherein the apparatus is so designed that no more than 3 l/m²h andpreferably no more than 1.2 l/m²h of binder are discharged during aspraying operation.
 4. Apparatus according to claim 1, wherein the spraynozzles are arranged along the binder line at intervals of no more than10 m, preferably no more than 8 m and in particular no more than 7 m. 5.Apparatus according to claim 1, wherein the spray nozzles for sprayingout the binder are designed with a circular or circular-segment-shapedspray cone, with the maximum distance between two adjacent spray nozzlesnot exceeding 80% of the diameter of this circle.
 6. Apparatus accordingto claim 1, wherein the binder reservoir provides the binder at amaximum pressure of 10 bar and preferably at a maximum pressure of 5bar.
 7. Apparatus according to claim 1, wherein the binder reservoirprovides the binder at a maximum pressure of 2 bar and preferably at amaximum pressure of 4 bar.
 8. Apparatus according to claim 1, whereinthe spray nozzles are so designed that the binder is sprayed with adroplet size of 30 to 120 μm and preferably 50 to 150 μm and inparticular with a droplet size of 60 to 90 μm.
 9. Apparatus according toclaim 1, wherein at least one spray nozzle is a pressure nozzle, whichopens automatically from a certain opening pressure of the fed binderupwards, or is combined with an automatically pressure control valve,and the apparatus has a pressure control, by which the pressure in thebinder line may be controlled.
 10. Apparatus according to claim 1,wherein the pressure control has a control valve which is fitted in thebinder line in the area between the binder reservoir and the pressurenozzle or nozzles and may be activated by a control unit.
 11. Apparatusaccording to claim 1, wherein the spray nozzle or nozzles is or areprovided with a valve which may be activated directly by a control unit.12. Apparatus according to claim 1, wherein the pressure vessel with gascushion has a feed line for filling the pressure vessel with gas cushionand a discharge line for draining the pressure vessel with gas cushion,wherein the feed line has a flow resistance compared to the dischargeline, e.g. a cross-section constriction, so that filling of the pressurevessel with gas cushion takes place with a lower volumetric flow thandraining of the pressure vessel with gas cushion.
 13. Apparatusaccording to claim 12, wherein the discharge line has a non-returnvalve, so that binder can flow through the discharge line only fordraining the diaphragm vessel.
 14. Apparatus according to claim 1,wherein the binder line has one or more pressure control valves which aspressure switching valves open from a predetermined switching pressureupwards and thereby release a binder feed to the spray nozzle(s) or aspressure regulating valves also open from a predetermined switchingpressure upwards and at the same time regulate the pressure on theoutflow side of the pressure regulating valve to a predeterminedpressure range.
 15. Apparatus according to claim 1, wherein severalpressure control valves are provided in the binder line and havedifferent switching pressures, so as to create sections with differentpressure levels in the binder line.
 16. Apparatus according to claim 15,wherein one or more pressure control valves are provided in a main runof the binder line, so that the main run is divided into sections withpredetermined pressure level.
 17. Apparatus according to claim 15,wherein one or more pressure control valves are provided in a branch runof the binder line diverging from a main run of the binder line, so thatthe respective branch run is closed if pressure falls below theswitching pressure, wherein the pressure control valves are preferablyin each case integrated with a spray nozzle.
 18. Apparatus according toclaim 1, wherein the binder line has one or more pressure reducers whichregulate the pressure on the outflow side of the pressure reducer to apredetermined pressure range, wherein the pressure reducer or reducersis or are preferably located adjacent to a spraying valve or integratedin a spraying valve.
 19. Apparatus according to claim 1, wherein thebinder line is made with an elasticity for elastic buffering of binderof at least 1% and preferably at least 0.5% of the total volume of thebinder line on the basis of pipe wall elasticity, at least one gaspocket and/or a diaphragm vessel.
 20. Apparatus according to claim 1,wherein the binder line is made with an elasticity for elastic bufferingof binder of a maximum 100% and preferably a maximum of 50% of the totalvolume of the binder line on the basis of pipe wall elasticity, at leastone gas pocket and/or a pressure vessel with gas cushion.
 21. Apparatusaccording to claim 1, wherein a control unit is provided which,depending on the filling state of the binder line, the filling state ofthe pressure vessel with gas cushion and/or the flow rate in the binderline, controls the feed of binder from the pressure vessel with gascushion into the binder line.